Teen Love on the Run or Abduction?

Are two teen lovers on the run, or was a girl taken to Mexico against her will?

Those are two scenarios police have considered to explain the disappearance of 17-year-old Adelene Ruiz, last seen Halloween night after leaving her job at the Swinging Door, a popular barbecue restaurant in Richmond, Texas, in her red Ford truck.

The girl was reported missing by her family, and an Amber Alert was issued Friday by the Fort Bend County Sheriff's Office. Authorities later discovered her abandoned car near the Swinging Door.

The same day, Ruiz's estranged boyfriend, Charlie Lucas Zelaya, 19, was expected in court for an appearance tied to a protective order Ruiz had filed against him after an assault incident. He failed to show up for the hearing.

Now investigators have issued a warrant for Zelaya's arrest on aggravated kidnapping, family violence and contempt of court charges, according to the sheriff's office. The local office of Crime Stoppers, an organization with branches around the world that aids local law enforcement, offered a $5,000 reward Saturday to any witnesses who could provide information that led to Zelaya's arrest.

"Along with a history of domestic violence, detectives have learned Zelaya is extremely possessive and controlling, and has threatened Adelene's life is (sic) she ever left him," the sheriff's office said in a release.

But Zelaya's family told ABC News' Houston affiliate KTRK that Zelaya and Ruiz were at the Zelaya house the night the pair went missing, and that the relationship was voluntary despite the protective order.

A Zelaya family spokesperson read a plea written by Zelaya's mother that asks the two missing teens to return to Texas.

"We have faith in you, Lucas," the statement read. "Your two families are in so much pain and suffering. Please, Lucas, please call someone and let us know that you and Adelene are OK."

Zelaya's mother also said that this is not the first time the two teenagers have run away together. Two years ago, she told KTRK, they spent two months together in Mexico.

Sheriff Milton Wright told local news Web site FortBendNow.com. that investigators are not entirely certain that Ruiz was taken against her will, but he said during a press conference that a witness heard Ruiz say, "Let me go, let me go," while she was at Zelaya's house.

"We do have information I can't release at this time that says they are in Mexico at this time," Wright told FortBendNow. "We do at this time believe she is being held against her will."

A call from ABC News to the Fort Bend County Sheriff's Office was not returned.

Zelaya is described as a Hispanic male, standing 5 feet 10 inches tall and weighing 175 pounds, with black hair and brown eyes. He is tattooed on both arms, as well as on his chest.

Adelene Ruiz was last seen wearing her work shirt, blue jeans and white sneakers.

The pair are believed to be in Zelaya's white 1999 Ford extended cab truck near Brownsville, the southernmost town in Texas, or in Mexico.