Paramedics evaluated one student for eye irritation after a small explosion in a life science lab Wednesday afternoon led to a precautionary evacuation.

According to a statement from the University, the explosion occurred at about 2:45 p.m. in the Life Sciences Annex — a section of the Clapp, Langley and Crawford Hall complex. A flame hood designed to limit exposure to toxic materials contained the explosion. Only one student needed medical attention, the statement said.

The buildings were evacuated as a precaution and reopened at about 3:30 mostly reopened. The first floor of the annex is still closed for cleanup. At least four fire trucks and three hazmat vehicles from the Pittsburgh Fire Department were on scene.

The 2:45 p.m. incident in the Life Sciences Annex in the Clapp, Langley and Crawford Hall complex is over and the building is reopened, excluding the first floor. pic.twitter.com/QqVUFaxfpG

— University of Pittsburgh (@PittTweet) January 31, 2018

At least four fire trucks, two foam trucks, three hazmat vehicles, two paramedics and four cops are on scene in front of Clapp after fire alarms went off in the building. Everyone was asked to evacuate. Police are not commenting on the cause yet. pic.twitter.com/xAFaga42UE

— The Pitt News (@ThePittNews) January 31, 2018

Junior neuroscience major Heather Smith’s class in Langley Hall was just wrapping up when the fire alarm went off. She said she hadn’t heard or felt anything but knew an false alarm had gone off earlier in the day, so she assumed it was “just another faulty alarm or fire drill.” But before she knew it, fire trucks, an ambulance and a hazmat crew had shown up.

“I feel like [with] Clapp, I kind of associate [it] with fire alarms, but they’ve always been minor or a drill, never anything of this magnitude,” she said. “Everybody was like, ‘This isn’t another ordinary day at Clapp.’”

Smith said she had an exam in her next class in the same room she had evacuated, but the professor ended up rescheduling it once the time reached 3:10 p.m.

“It was at first going to be Monday, but my professor took pity because of the Super Bowl,” she said.

Senior microbiology major Aisha Kanneh was in her microbiology seminar in Langley and said she didn’t hear any explosions prior to the fire alarm going off. She knew about the alarm from earlier in the day and assumed that it was “just another drill.” She left her belongings in the classroom and filed out with the rest of her class.

“We realized soon, ‘Oh, this is real,’” she said. “We’d all left our stuff behind, so we hung around for 45 minutes until we could get it.”

Kanneh said when she and her classmates re-entered the building, they couldn’t find their professor, who had the key to the locked room with their belongings.

“One of our classmates went to the front desk and got the key for the door,” she said. “We left him a note on the board and left.”

Kanneh said she’s had plenty of classes in Clapp before when the fire alarm has gone off, but it’s always been a drill.

“I’m pretty sure the last time I was in there and there was an alarm, they told us not to evacuate,” she said. “I think it was my junior year, fall semester, something happened with the fire alarm.”

Sylvia Freeman, a junior biology and art major, was present for both fire alarms that went off Wednesday. When the second alarm went off, she was in the library in Langley and assumed it was a mistake.

“Most people assumed it was false, I think,” she said. “I went outside for about five minutes and then went into Alumni Hall to keep studying.”

Ayesha Godiwala, a junior biology major, was in an auditorium in Langley when the alarm went off. She said she packed her things and left for Hillman because it was her last class of the day. She wasn’t alarmed, though, because she had a similar experience in Langley recently.

“There was another alarm last week,” she said. “I was like, ‘Oh, here we go again.’”