TULSA, Oklahoma - New details are emerging after nearly 40 people were mysteriously sickened Thursday afternoon.

Some elementary school students on a field trip at the Tulsa County Jail all came down with the same symptoms.

The Tulsa fire department says it has completely cleared the jail as the source of anything that could have sent nearly 40 kids and adults to hospitals Thursday with headaches and stomach aches.

Sick students and panicked parents.

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

During a tour of the jail, 31 Bell Elementary students and 7 adults with their group got sick within an hour. They had all the symptoms of carbon monoxide poisoning, but that's still speculation.

"We ended up taking a total of 20 kids in a matter of minutes," said Dr. Michael Smith, St. John Health System ER.

Dr. Michael Smith at St. John kept the kids on oxygen and drew their blood.

"My diagnosis on these kids was chemical exposure," Dr. Smith said.

Dr. Smith says all the patients had slightly elevated carbon monoxide levels. 1. 5 are normal and the kids all had levels of 1.5 to 2.4.

"They all were consistently raised, which tells us they were probably exposed to some level of carbon monoxide somewhere," Dr. Smith said.

All of them were treated and released in less than an hour. Five hours after the jail partially evacuated, the fire department cleared the jail as part of the investigation.

"It takes a certain period of time for CO to cycle out of your system," Tulsa Fire Chief Captain Alan Barnes said. "So they could have been exposed yesterday or last night or the day before."

The elementary school kids were on the tour to learn about different careers - and in an unusual twist, they got to see several jobs play out, unfortunately at their own expense.

The fire department also couldn't find anything on the sheriff's bus that transported the kids to the jail this morning. So as of Thursday evening, still no answer as to how the students got sick.