Fifteen-year-old Elizabeth Thomas has been missing for nearly a week.

Investigators are trying to find the teenager and the person they believe kidnapped her — a 50-year-old man who used to teach at her school.

“And, you know, our Amber Alert is ongoing and it has been several days since anyone has seen Elizabeth Thomas or Tad Cummins. And our concern is growing. We want her home, and we want him in custody.”

There have been more than 250 tips so far, but none have produced results. And there have been no credible reported sightings of either Elizabeth or her teacher and suspected abductor, Tad Cummins.

They were both last seen last Monday morning in Columbia, Tennessee.

Investigators last placed Elizabeth in Decatur, Alabama on Monday afternoon. Now they believe the pair could be anywhere nationwide.

Cummins’ wife appeared at a news conference, pleading for her husband to turn himself in and not harm Elizabeth.

“My heart breaks for the family of Beth Thomas…Tad, this is not you. This is not who you are. We can help you get through this.”

Investigators uncovered a troubling pattern of behavior they say indicates Cummins had been using his role as Elizabeth’s teacher for some time to manipulate her in “an effort to lure and potentially sexually exploit her.”

These are recent surveillance images of Cummins. He is a white male, six feet tall, weighing approximately 200 pounds. He has brown hair and eyes.

Cummins is believed to be armed with two handguns and is driving a silver Nissan Rogue with the Tennessee license plate 976-ZPT.

The FBI is helping in the search. Anyone with information is urged to call 1-800-TBI-FIND.