It’s a highly secured, sophisticated research lab studying deadly diseases such as bird flu, monkeypox, tuberculosis and rabies.

It’s in a facility called Building 18, which cost taxpayers $214 million.

And now, the Biosafety Level 3 lab at the Centers for Disease Control and Prevention in Atlanta is also the subject of a congressional investigation after a potentially dangerous airflow leak at that lab, CNN has learned.

The leak occurred on February 16, when air flowed the wrong way out of a germ lab into a clean-air corridor, rather than through the powerful HEPA filter that cleans the air, congressional sources and CDC officials said. Visitors touring the facility were in the clean corridor when they observed a puff of air being pushed out from the lab through a slot in a door window.

If experiments had been under way at the time of that air leak, experts say, unprotected visitors could have been exposed to deadly germs, although an epidemic would have been unlikely.

According to U.S. Rep. Michael Burgess, a Texas Republican and a medical doctor, the House Energy and Commerce Committee has asked the CDC for documents about that incident. The request came in the wake of a report on internal CDC e-mails about the incident, first reported by USA Today last week.

“The biggest concern was that there was a contingent of visitors who were walking through the building,” Burgess said. “And had one of those people been stricken or made ill or worse, obviously that would have been devastating.”

The lab handles small mammals such as rats, ferrets and mice as part of its experiments with pathogens, according to CDC officials. They say animals were in the lab at the time of the air leak, but they were secured in filtered cages.

CDC officials say the lab was clean, was not active at the time, and no one got infected.

READ MORE: CNN