TULSA, Oklahoma - Part of the Tulsa County jail was evacuated today after children, who were there on a field trip, got sick. Worried there could be dangerous fumes, the jail did a partial evacuation.

The children were from Bell Elementary, most about 12 years old, on a career day field trip.

Paramedics loaded 31 students into ambulances and sent them to hospitals for treatment.

Seven parents and teachers were transported as well.

All had the symptoms of carbon monoxide poisoning, but the fire department said it didn't believe that was the cause.

"We've been told the jail doesn't have any gas running throughout the facility so right now the fire department is trying to determine what led to some elevated readings on our CO detectors," TFD's Tim Smallwood said.

Whatever it was made both children and some parents sick, but after the building was evacuated - firefighters were unable to detect anything hazardous.

They were in a classroom training area when it happened.

"This is just in the non-secure portion of the jail, which we consider the administrative offices of the jail," said Shannon Clark of the Tulsa County Sheriff's Office.

The Fire Department and EMSA checked all of the children, but 15 of them had no problems and were sent back to school.

They were loaded onto a prison transport bus for a while, then taken back to Bell Elementary where they were picked up by their parents at the end of a very unusual school day.

Back at the scene, some parents arrived to look for their children and were sent to the hospital.

"They said she's OK, but I need to make sure she's OK," parent George Figueroa said.

The number of patients and the possibility it could have affected the entire jail prompted a huge response from EMSA and the fire department.

But authorities said the problem was limited to the area housing the administrative offices.

St. John Hospital reports all of the children treated had elevated levels of carbon monoxide and they've all been released from the hospital.

The fire department was unable to find anything inside the jail, or on the bus that might have given off the fumes.