OMAHA, Neb. -- Authorities were searching on Thursday for a 13-year-old boy and a female middle school teacher believed to be on the run after police began investigating an alleged intimate relationship between the pair.

Kelsey Peterson, 25, a sixth-grade teacher and basketball coach at Lexington Middle School, was placed on administrative leave last week. A judge issued an arrest warrant Monday charging her with kidnapping, child abuse and contributing to the delinquency of a minor.

Authorities believed the two were traveling together in Peterson's car and police nationwide were notified about them. Court documents said the boy was last seen Oct. 26.

"We're still focused on locating both of them, whether they're together or not," Dawson County Attorney Elizabeth Waterman said Thursday. "I think right now anything is possible."

The boy was a student at the school, but it was not clear if Peterson was his teacher.

Court documents showed authorities had recovered several e-mails and letters in which the two 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 court documents.

Court documents say Peterson's school-issued laptop contained letters to the student, including one from April saying she loved him, thought he loved her, was "100 percent faithful" to him and would always be faithful.

Police said the boy contacted his family over the weekend and said the two were in Grand Island, about 85 miles east of Lexington, according to court documents. Police also said the pair were apparently spotted Friday night at a Denver convenience store, then again Sunday in Ogallala, in western Nebraska near the northeast tip of Colorado. Police on Thursday referred questions to Waterman, who would not say where police were focusing their search or comment on reports about where the pair were spotted.

A message left for Todd Chessmore, the school district's superintendent, by The Associated Press was not returned Thursday. A Lexington Middle School official referred questions to Chessmore.

Lexington, a farming and meatpacking town of about 10,000, is about 220 miles west of Omaha in central Nebraska.

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