PHILADELPHIA (CBS) – The FBI says a Rider University professor was arrested at Philadelphia International Airport Monday, caught in a online “sting” when he allegedly tried to lure a mother and her 13-year-old daughter from Idaho to have sex with both of them.

Dr. Austin Winther, who lives in Mount Airy, was arrested as he arrived at an airport gate thinking he was meeting with the mother and daughter with whom he had contact online for nearly five months, allegedly exchanging lurid emails.

Dr. Winther, according to Rider officials, began teaching there in 2005 until going out on a long-term disability leave in October 2009. The officials say he taught only adults in the Graduate School of Education.

Following his initial appearance in federal court, Dr. Winther was held without bail in the Federal Detention Center to await a hearing Friday that will determine if he will be kept behind bars until trial.

In one email, cited in the arrest warrant, the suspect allegedly wrote about several other trips and meetings in other cities with girls whose ages are not specified.

The FBI says its investigation is continuing.

Reported by Walt Hunter, CBS 3