Police tape hangs across the street in front of a house Feb. 26, 2005 in Park City, Kansas. Getty Images

The alleged relationship between missing Tennessee teenager Elizabeth Thomas and adult teacher Tad Cummins was not a "romance," authorities said Tuesday as the case stretched into its third week. Elizabeth was a victim, according to Tennessee Bureau of Investigation Director Mark Gwyn, and law enforcement officers were determined to bring her home, the Associated Press reported.

"She is 15, a child. He is 50, a grown man. She's a high school freshman. He's a former teacher. This is, and was, not a romance," Gwyn told reporters, according to WBIR. "This was manipulation solely to benefit Tad Cummins. This is not a fairy tale. This is a case of kidnapping."

Read: Tennessee Student Believed To Be Kidnapped By Teacher Tad Cummins

Cummins and Elizabeth vanished March 13, a month after a student saw them kissing at school and a week after the man searched the internet for "teen marriage," the Tennessean reported. Police have received more than 1,000 tips about their disappearance but have not located the girl. Cummins, who was believed to be armed, has been charged with aggravated kidnapping and sexual misconduct with a minor. He has also been fired from his job at Culleoka Unit School.

The school had been investigating the duo's relationship before the abduction, but Elizabeth and Cummins insisted they didn't have any inappropriate interactions, according to CNN.

Read: Missing Tennessee Teen Knew Something Bad Would Happen

One of Elizabeth's friends dropped her off March 13 at a restaurant; Cummins was spotted nearby filling his gas tank. Investigators initially thought they'd fled to Alabama, but the bureau revealed they now suspected the couple could have gone to Mexico, according to the Tennesseean. ABC News reported that law enforcement in Mexico and Central America had been alerted about the duo.

The bureau also tweeted a Spanish translation of Elizabeth's missing flier Wednesday and asked viewers to help share it. "We don't know how much publicity it's getting, and we need people down there to know who they are," District Attorney General Brent Cooper said.

If you see Cummins or Elizabeth or have information about them, you're asked to alert 1-800-TBI-FIND or 911.