The teacher accused of fleeing to Mexico with a 13-year-old boy after reports surfaced that they were having sex was popular but strict with kids who got in trouble, students said Sunday.

Kelsey Peterson, 25, and Fernando Rodriguez, the subjects of a weeklong search, were taken into custody without incident in Mexicali, Mexico, after the boy's relatives told police he had called home asking for money.

Peterson, a sixth-grade math teacher and basketball coach at Lexington Middle School, was turned over to FBI agents early Saturday. She was being held on federal charges at the Imperial County Jail in El Centro, California, and was expected to appear before a U.S. magistrate judge on Monday.

"The judge will advise Ms. Peterson of the charge (allegation) against her and her specific rights," FBI Special Agent Darrell Foxworth in San Diego said in a statement Sunday. He said he had no updates on the case and there was no immediate indication if she had a lawyer to comment for her.

Fernando was turned over to relatives in Mexico. He was an illegal immigrant while residing in the United States, and might not be able to return to the rural Nebraska town where he was an eighth-grader.

The boy's aunt, Laura Rodriguez, who has been speaking for the family, did not answer calls to her Lexington home and cell phone on Sunday. Nobody answered the door at her house, although three vehicles were parked in the driveway and a man could be seen through a window.

A seventh-grader at Lexington Middle School, Gage Timson, said he knew Fernando through friends and hung out with him a couple of times.

He also described Peterson as "kinda cool sometimes" — although she could be strict when kids got in trouble.

Dalton Wamsley, 14, started sixth grade the same year Peterson began teaching sixth-grade math at the school.

"After school, kids hung out around her (classroom)," Dalton said. "She was like nice, friendly, easy to talk to."

Fernando's family agreed with authorities to send him to the family's home town in Mexico's southern state of Guanajuato to be near his grandmother, uncles and father, said one uncle, Pedro Raya.

Alfredo Arenas, the Baja California state police official who detained Peterson, said the pair had a mutual agreement to flee after stories surfaced that they were having sex surfaced.

The Associated Press generally does not identify people who may be victims of sex crimes, but the boy's name had been widely publicized as police searched for him.

Authorities in Mexico said Fernando told police of vague but romantic plans with Peterson — to scrap normal teenage life for a life of hiding in southern or central Mexico.

Peterson is charged in Nebraska with kidnapping, child abuse and contributing to the delinquency of a minor. She also faces federal charges of transporting a minor across state lines or a foreign border for sexual activity, U.S. Attorney Joe Stecher said.

Peterson has an 8-year-old daughter, but the school district's superintendent has declined to give any details about her and it was not clear where the girl was staying.

Stecher said he would work with Dawson County Attorney Elizabeth Waterman to decide in which jurisdiction she would face charges.

Waterman said she knew about Fernando's immigration status but did not know how it was going to affect her case against Peterson.

Court documents showed authorities had recovered several e-mails and letters in which Peterson and the boy professed their affection for one another.

In letters, the boy called Peterson his "Baby Gurl" and said their relationship was "just not about the sex but that it was pretty good," according to the court documents.