For parents waiting for news of their missing children, some of whom disappeared from their homes and others on walks around their quiet neighborhoods, each day is filled with both hope and heartbreak.
It's an agony that is shared by police departments who are often in a race against time in their desperate search for leads .
ABCNews.com is following five of the most high-profile cases, and here's an update on where the investigations stand. If you have information on any of these cases, call the local police department.
Haleigh Cummings: Missing Since Feb. 10, 2009
Five-year-old Haleigh Cummings disappeared from her father's Satsuma, Fla., home in February 2009. The last person to see the curly, blond-haired girl was her babysitter, Misty Croslin, who was then just 17-years-old.
This past week, the investigation into her disappearance heated up again as the Putnam County Sheriff's office commissioned as many as 40 divers to search a murky river just five miles from where the girl was last seen. A tip, investigators say, had led them to the river to search for clues in the case.
Late Thursday, Sheriff Jeff Hardy declared that he believed Haleigh was "likely dead" and that investigators would keep working the case until justice was served. Hardy also said that authorities have identified "several" persons of interest in the case for the first time in the 14-month investigation.
Hardy did not release the names of these persons of interests to the public, citing the ongoing investigation.
Haleigh was first reported missing by her father, Ronald Cummings, who made a chilling 911 call, telling a dispatcher, "If I find whoever has my daughter before you all do, I'm killing them. I don't care if I spend the rest of my life in prison."
Croslin and Ronald Cummings, who have married and divorced in the past 14 months, are being held in separate Florida jails on charges of drug trafficking, crimes that are unrelated to Haleigh's disappearance.
Croslin's cousin, 20-year-old Joe Overstreet, was also interviewed by investigators this week in Nashville, Tenn., where he lives. Overstreet had been visiting Haleigh and Croslin when the girl went missing. He has denied any involvement in her disappearance and has never been charged.
Kayleah Wilson: Missing Since March 28, 2010
The 12-year-old is a sixth grader and was last seen wearing a white-and-pink shirt over a white tank top, blue jeans and white and red shoes. She is described as being 5 feet 1 inch, and approximately 145 pounds with brown eyes and brown hair.
Late Thursday, the FBI doubled the amount of reward money they are now offering from $10,000 to $20,000.
Investigators say they are becoming increasingly convinced that Kayleah was abductedand urged members of the community to be aware of individuals who may behaving strangely, such as someone having trouble sleeping or expressing an unusual interest in the case.
Investigators from the onset have said they have little information as to where the tween may be.
"It's very unusual not to have any indication to point us in a direction one way or another," Greeley Police Chief Jerry Garner said.
Kayleh's mother, April Wilson, told ABCNews.com that this is not typical behavior for her daughter and that she never suspected anything out of the ordinary when she said goodbye to her daughter before she left for the party.
She walked over to the couch and said, 'I love you,' and 'I'll be home by 7,' and she walked out the door and that was it," Wilson said. "She had been talking about the party. She was really looking forward to it."
Brittanee Drexel: Missing Since April 25, 2009
Brittanee Drexel was 17-years-old when she went missing from Myrtle Beach, S.C. in April 2009.
There for a spring break trip her mother had forbidden, Brittanee was seen leaving the BlueWater Resort visiting a group of Rochester-area men after having a falling out with the friends she'd originally accompanied to the popular spring-break destination.
Earlier this week, investigators announced that they had identified as many as four persons of interest in connection to Brittanee's disappearance.
But with the new information came discouraging news for Brittanee's family, who were upset that authorities said publicly that they do not think the teen is still alive.
"Based solely on the information we have right now, we do not feel like she is alive," Georgetown County Sheriff's Office spokesman Lt. Neil Johnson said.
Brittanee's mother, who has said she didn't want her daughter going on the trip because there were no adult chaperones, told ABCNews.com that she still believes her daughter is alive, and plans to head to South Carolina to continue to search for her.
"We're still hoping she's alive, yes," Drexel said. "I think it was a little premature and I find it appalling that [the police] don't think she's alive."
Drexel said that while authorities have given her little information about the people of interest, she believes they are locals from the Myrtle Beach area and not friends of her daughter's from New York.
"I think that Brittanee either could have been trafficked or someone is holding her against her will," Drexel said. "I'm hoping she'll be strong enough to get away or we'll be able to find her."
The girl's aunt, Keri Drexel, introduced a set of playing cards featuring her niece and other missing children. The decks are being distributed to inmates in the Florida prison system hoping someone will know what happened to Brittanee and will be willing to speak up.
Lindsey Baum: Missing Since June 26, 2009
Lindsey Baum, 10, was walking home from a friend's house in the small town of McCleary, Wash., in June 2009 when she vanished.
The 10-minute walk down a heavily populated suburban street between her house and a friend's was one she did often, and had never concerned her mother, Melissa Baum.
Baum is convinced her daughter was kidnapped and still believes she is alive.
The FBI has so far identified 12 persons of interest in the case, inside and outside of McCleary, with at least two people of high interest.
Grays Harbor County Undersheriff Rick Scott told ABCNews.com that investigators are still combing through a "tremendous amount of information" they gathered during a two-week search for the girl in March.
"At this point, we still have no concrete information into her disappearance," said Scott. "I will always have hope she's alive until there is evidence that clearly states the contrary."
"Statistics suggest that's highly unlikely but every time you find a girl who lived for 18 years in someone's backyard it gives you hope that this will be one of those cases," he said, referencing the miraculous discovery of Jaycee Dugard, who was rescued after being held captive by her abductor in California.
Baby Gabriel Johnson: Missing Since Dec. 27, 2009
Gabriel Johnson, known most simply as "Baby Gabriel," was last seen with his mother, 23-year-old Elizabeth Johnson, at a San Antonio, Texas, park.
Johnson was arrested on Dec. 29 in Miami Beach, Fla., for interfering with court-ordered custody agreements, but Gabriel was nowhere to be found.
Gabriel Johnson's biological father, Logan McQueary, has said that he fears Elizabeth Johnson may have killed their son, despite the lack evidence. But a couple who had been in talks to adopt the baby are sticking by the Arizona mother, saying she hid Gabriel to protect him after her husband refused to let her put him up for adoption.
Johnson is now in a Tempe, Ariz., jail and faces kidnapping, child abuse, custodial interference and conspiracy to commit custodial interference charges after she allegedly sent text messages to the boy's biological father, Logan McQueary, that she had killed their son and left his body in a dumpster.
Johnson later changed her story and said she gave the baby to a random couple she met in a San Antonio park.
She is currently being held on a $1.1 million bond while investigators search for signs of baby Gabriel.
Nadia Bloom, Found Alive After Days, Gives Hope to Others
The story of 11-year-old Nadia Bloom, who after more than four days of searching was eventually found alive in the swamplands near her Winter Springs, Fla., home earlier this week, is one that will likely stand as a beacon of hope for parents struggling with the disappearance of their own children.
Bloom, who is mildly autistic, never returned home after taking a bike ride around her house. Investigators found her waist-deep in swamp water after getting disoriented in the woods near her home while on a hunt for "treasures."
"She's doing great, she really is," said Tanya Bloom, Nadia's mother, at a press conference. "It's a story you don't usually get. It's a story of hope."