A liquid nitrogen leak occurred at the University of Wisconsin Chemistry Building Monday night.

The Madison Fire Department Hazardous Incident Team contained the leak and a technician made the final repairs to stop the nitrogen, according to a Madison Fire Department statement. The University of Wisconsin Police Department evacuated the building and no one was injured, the statement said.

A passerby in the area alerted the Madison Fire Department to the leak and the fire department arrived on the scene at 6:39 p.m., according to the statement.

MFD Spokesperson Eric Dahl said the fire department does not know when the leak started. They were made aware of the incident after a 911 call, he said.

“The first we found out about it was when we got the 911 call,” Dahl said. “A passerby saw a vapor cloud leaking out next to the building.”

Firefighters called a technician from a local industrial gas company that supplies liquid nitrogen to assist with stopping the leak, according to the statement. The firefighters followed the technician’s instructions to slow the leak before he arrived, the statement said.

UWPD evacuated occupants of the building and limited access to the surrounding area, the statement said. People were allowed to reenter the building after firefighters used gas monitors to determine the safety of the air quality, the statement said.

The nitrogen is not poisonous, the statement said, but it can cause rapid suffocation and extreme frostbite.

Dahl said there were no noticeable effects to the Chemistry Building or the surrounding area.

“When I spoke to the chief who was on the scene they did not indicate that there was any damage [to the chemistry building],” Dahl said.

At this time, Dahl said no one knows how the leak began. UWPD and UW Safety personnel are currently working on assessing the cause of the leak, he said.