GAINESVILLE, Fla. -

An Alachua County teacher and swimming coach is accused of having inappropriate relationships with children.

Gainesville police said 31-year-old Joseph Diaz asked a now-15-year-old boy to take nude pictures of himself using Diaz's phone.

More alleged victims have since come forward.

Diaz was arrested Thursday, accused of having child pornography and promoting it with a minor. That stems from the inappropriate relationship with the boy, investigators said.

Diaz was released from jail on bond Friday and then was arrested again because police said more potential victims came forward.

Detectives said there are three underage victims, and the crimes are believed to have been going on for years.

According to records, Diaz was a swimming coach at the Makos Aquatics Club, as well as a behavior resource teacher at High Springs Community School. Investigators said he had an inappropriate relationship with one boy for several years, asking the child to take nude pictures and videos of himself on his cellphone.

"Our investigation revealed that this relationship began when the victim was 11 years old and has progressed to the point where there have been photographs taken of the young victim by the defendant's cellphone," Officer Ben Tobias said. "At this point there has not been any allegedly sexual contact between the two, but the investigation is definitely on going to see exactly what has transpired over these four years."

Detectives are worried there may be more victims and are asking for anyone who may know anything about Diaz to come forward. The Department of Children and Families is also investigating.