HOUSTON -

An infectious disease specialist is trying to determine if there's a link between two teenagers who died and a third who is in critical condition after they contracted similar flu-like symptoms.

The teenagers who died were from Liberty and Montgomery Counties. The third teenager is being treated at Texas Children's Hospital.

"All of the sudden, the child having the respiratory problem -- respiratory failure -- and ending up in critical condition," said Dr. Syed Ibrahim. "That is very unusual."

All three teenagers attended different high schools but had fevers, coughing, and shortness of breath. Two of the teenagers suffered from seizures.

Ibrahim said tests for meningitis, encephalitis, and rabies came back negative.

"So far, I have not heard back any connection between the three of these cases," he said.

The Centers of Disease Control is analyzing tests submitted from Montgomery County Health Department on the teenagers.