With the TV on around the clock in her Atwater, Calif., home, Tokiko Harper is desperate for any sliver of news she can get about her 84-year-old sister Kazuyo Komatsu.
"I don't have much of a hope," she told ABC News, her voice cracking. "My sister is old and she was probably alone at that hour. I am afraid."
Harper is just one of the presumably hundreds of people in the United States who are seeking any information on family or friends now missing in Japan. The official death toll following Japan's huge 8.9 earthquake and ensuing tsunami Friday had reached 686 by Saturday afternoon and could eventually reach 1,000 according to officials there.
The State Department's Consular Task Force alone has reported receiving "thousands" of inquiries, according to spokeswoman Julie Reside, who did not provide an exact number.
"We have accounted for many U.S. citizens in the Sensei and Miyagi areas, and continue our efforts to locate others," Reside told ABC News. "U.S. citizens are not required to sign up with the Department when they go abroad, so we do not have an exact count of U.S. citizens in the region."
The United States Agency for International Development is sponsoring the travel of urban search and rescue teams from Fairfax, Va., and Los Angeles.
Americans Missing in Japan Earthquake: Sporadic, Fleeting Contact
Several Americans who have heard from their loved ones said they still remain deeply concerned for their well being.
Phyllis Phelan of Southbury, Conn., said she has been in touch with her son Tim, 53, a university professor in Sendai whose wife is Japanese, but contact has been fleeting and sporadic.
"We have not heard from him since yesterday. He was using his iPad and was not saying much, to save the battery," she told ABC News late today. "We're worried. He's without power. It's cold there and we're concerned about all of her family: brothers and sisters and nieces and nephews."
Marco Alvarez of Los Angeles was on the phone with his brother Omar, who lives in the coastal city of Sendai, at the exact moment the earthquake struck. They re-established contact after the quake but after the tsunami hit, Omar disappeared.
It wasn't until a full, nerve-wracking day later that Marco Alvarez received a text message from his brother, a former Marine whose wife is Japanese, saying the couple and their daughters were OK.
"He had to go up a mountain top to get reception on his cell phone," Alvarez told ABC News.
In the five minutes the brothers were able to talk before the call was dropped, Omar Alvarez reported that they don't have electricity or water, people are out in the streets scavenging and there are fires dotting the skyline, Marco Alvarez said.
But just hearing his brother's voice was enough to keep him going for another day.
"It was," he said, "a freakin' load off my back."
With additional reporting by Ursula Fahy