The UW Engineering Research Building was evacuated today after occupants noticed an ammonia leak in the 9th floor lab where they were working.

City of Madison firefighters were dispatched to 1500 Engineering Dr. on the UW campus at 11:22 a.m. The Department's Hazardous Materials team also responded to monitor conditions and offer advisory assistance.

UW Police officers were first on scene. They activated a pull station to alert occupants to evacuate and shut the doors to the lab in an effort to contain the leak.

Engineering Drive was closed to traffic for about an hour between Randall Avenue and Camp Randall Stadium.

Firefighters entered the building and shut off the 20-pound ammonia tank that was the source of the leak. The leak was contained to two adjacent labs. The building's air handling system is sufficient to clear the remaining fumes within 30 minutes. The building was returned to the university at 12:20 p.m. and the incident was terminated.

There were no injuries.