Updated: A Vanderbilt Children's Hospital spokesperson said doctors treated more than two dozen Drexel Preparatory Academy for carbon monoxide exposure.

Officials at the Tennessee Poison Center want parents to be on the lookout for the tell-tale signs of exposure to the potentially deadly gas.

"If they have a headache, vomiting, nausea, throwing up, if they had any symptoms now that they didn't have [Monday] when they went into school then those are the children that we would be most concerned about," said Dr. Donna Seger, medical director for the Tennessee Poison Center.

Seger said just after 2 p.m. Vanderbilt Children s Hospital admitted patients that were students at Drexel Preparatory Academy in Whites Creek that may have been exposed to the gas that can be lethal in high doses.

"A carbon monoxide detector went off that caused concern," Seger said.  "There have been a number of children that have been symptomatic potentially of carbon monoxide exposure"

 Drexel is a K-4 charter school on Jackson Road in Whites Creek.

" The school first broke the news to parents over the phone," Seger said.

A Metro Schools tweet followed at 4:34 that read, "If your child attends Drexel, please take him or her to an emergency room for an evaluation. "

A Vanderbilt Children's Hospital spokesperson says 49 students were evaluated and 40 were confirmed and treated.

"The children will be admitted for a 23-hour observation and will be discharged tomorrow," Seger said.  "If there are any subsequent problems it would be very unusual"

All of the children were in stable condition Monday night, according to a spokesperson for the Children s Hospital.

Calls to the school were not returned.

School will be closed there on Tuesday.

If you feel your child may have been exposed, you are urged to contact the Poison Help Hotline at 1-800-222-1222.Update : 40 Children Treated for Carbon Monoxide Exposure - Eric Alvarez