TALLAHASSEE — A criminal investigation is under way regarding allegations that a guard at a juvenile detention facility in Okeechobee County had sex with one of the facility's detainees, state officials said Thursday.

The investigation began last month after guards at the Okeechobee Juvenile Offender Corrections Center found love letters allegedly written by the female guard and the detainee, now 18, whose mother says he is mentally retarded. The letters allegedly detailed the sexual relationship in the detainee's cell.

Mike Powers, a spokesman for G4S Youth Services, a Virginia-based company that has a contract with the state to operate the corrections center, said the company contacted the Okeechobee sheriff's office and state juvenile justice officials.

"We're certainly aware of the allegations and from the moment they surfaced we've been cooperating fully with the sheriff's office and the department's inspector general," Powers said.

Department officials refused to release the names of the guard or guards involved, but Okeechobee County sheriff spokesman William Markham said Thursday that guards Sheila Snell and Pamela Watson were investigated.

Okeechobee closed the investigation without charging anyone, however, because the victim refused to cooperate, Markham said.

Department of Juvenile Justice officials referred questions about the investigation to Bruce Colton, state attorney for Okeechobee County and the Treasure Coast. Powers said he was unaware of the state attorney's investigation, and Colton's office could not be reached for comment.

Lawyers for the detainee, who has been in Department of Juvenile Justice custody for three years, filed a public records lawsuit against the department Thursday, alleging that the state has refused to hand over the letters to cover up the alleged wrongdoing.

In a statement issued late Thursday, department officials said the records are exempt until the investigation is concluded.

"There currently is an active criminal investigation into an allegation of sexual contact between a staff member and a youth at a DJJ facility. I am concerned and outraged that this behavior may have occurred and take the accusations very seriously," said the statement, attributed to Department of Juvenile Justice Secretary Anthony Schembri.

The "staff member allegedly involved in the matter has been terminated," the statement said.

But Powers said Thursday evening, "Nobody got fired. One employee had resigned a month before these letters were found and another one is still working there."

The detainee told his attorneys, Benjamin Crump and Daryl Parks, and his mother that he has had sex with at least five guards in three different facilities, the lawyers said at a news conference Thursday that included the detainee's mother and state Sen. Tony Hill.

The guard who allegedly wrote the letters is pregnant, Crump said.

"My son was sent to these facilities to get help, and not to come out being raped, abused and a father of a child from a guard," said the mother, of Clermont, in Lake County. She said her son is mentally retarded and has behavioral problems.

Parks and Crump also represent the parents of 14-year-old Martin Lee Anderson, who died after a beating by boot camp guards in Bay County. Anderson's parents also went to court to get a judge to order the agency to release a videotape of the beating.

"It certainly reminds you of the Martin Anderson videotape," Crump said. "When there's something that is not good or damning or shows you that suspicious activities are going to be uncovered, they do everything in their power to conspire not to let the truth out. This has to stop."

An autopsy by the Bay County medical examiner found that Anderson died of complications from sickle cell anemia trait, but a subsequent autopsy by the Hillsborough County medical examiner found that he was suffocated to death. The second autopsy was done after Gov. Jeb Bush took local and state officials off the case and ordered the Hillsborough County state attorney to investigate. That investigation continues, and no charges have been filed.

Hill, D-Jacksonville, said he plans to ask Bush to conduct an internal investigation to determine what is wrong at the agency, which oversees more than 54,000 youths statewide.

"It's just appalling. It's appalling," said Hill. "Apparently something has run amok. Something is going on that needs to be addressed."