The Nanaline H. Duke Building on Research Drive was unoccupied when a fire alarm sounded on the second floor at 6:17 a.m., according to Assistant Fire Marshal Eddie Reid.

Although an investigation into the cause of the fire has not yet been completed, Reid said investigators determined the fire was not intentionally set.

Freezers containing "compounds with low levels of radioactive materials" had been stored in the lab and sustained some heat damage, Duke Police spokeswoman Leanora Minai said, but were removed from the lab before catching fire.

Wayne Thomann, director of Duke's Occupational & Environmental Safety Office, determined that no radioactivity had been released, Minai said. Samples taken from the lab area came up negative for contamination, although officials will continue to "monitor and evaluate" the building, she added.

Thomann was not available for comment. "The Occupational & Environmental Safety Office is very comfortable that there is just no [possibility of contamination]," Minai said.

The approximately 1,000-square-foot lab sustained extensive damage and will likely require renovation, according to Minai. Smoke and water also damaged rooms adjacent to and below the lab, she said.

The Nanaline H. Duke Building has endured at least one blaze in the past, according to the university. In 1998, the third floor of the building caught fire after a coffee machine was left on over a holiday vacation.

Constructed in 1968, the 33,000-square-foot building houses several of the university's science departments.

Although Monday's fire was quickly doused, Research Drive was closed for several hours in the aftermath of the blaze.