A fire late Friday night sent thick black smoke into the air and caused extensive damage to the Biological Research Infrastructure (BRI), an underground laboratory facility that is currently under construction.

The BRI, located in the courtyard of Harvard’s Biological Laboratories on Divinity Avenue, was closed and empty at the time of the fire, according to the Harvard News Office. There were no injuries.

University Operations Services (UOS) received an alarm signal at around 11 p.m. on Friday night and dispatched firefighters to the scene, who fully extinguished the fire within two hours.

According to the UOS daily maintenance log, the fire occurred in an electrical vault containing construction materials, debris, and flammable chemicals.

The Cambridge Fire Department (CFD) is currently investigating the exact cause of the fire.

General Superintendent for the BRI project, Victor M. Pereira said, “We are not sure what the origin was,” but added that he had heard the fire was possibly caused by a light bulb.

“I’m sure every aspect of what could have caused this to happen will be explored,” said Robert Mitchell, director of Faculty of Arts and Sciences (FAS) communications.

CFD’s Deputy Chief John Gelinas told the Associated Press that fire fighters faced “zero visibility” and that they had to use ropes to descend into the underground site.

Gelinas estimated that the fire caused more than $1 million in damages to the construction site, according to the Associated Press.

Smoke from the fire also seeped into the surrounding labs. The CFD and Harvard’s Environment Health and Safey officials cleared the building for occupancy by 3 a.m. Saturday morning after carbon monoxide testing, according to the UOS maintenance log. Approximately 250 people work in the labs during a normal weekday.

Pereira said that construction workers were able to get into most of the site on Saturday morning to begin cleanup.

The BRI is a two level facility that, when complete, will contain 75,000 square feet of research space and 16,000 cages for laboratory mice. The facility was scheduled to open for genetic research in June. Harvard officials said that there was smoke damage to the construction site, and it was unknown what delays the fire might cause.

—Staff writer Evan H. Jacobs can be reached at ehjacobs@fas.harvard.edu.