Oct. 26 (Bloomberg) -- Harvard Medical School is increasing security in its laboratory buildings after a toxicology report revealed that six researchers who fell ill Aug. 26 had drunk coffee tainted with the chemical sodium azide.

“We’re looking at this situation very carefully and reviewing the security precautions,” David Cameron, a spokesman for the Boston-based medical school, said in a telephone interview today. The school is in the process of installing additional closed-circuit TV cameras, he said.

“It’s a laboratory, so we have to ensure the researchers can still do their work,” Cameron said.

The six workers all drank coffee from the same coffee maker in the New Research Building and felt symptoms of low blood pressure and dizziness, the Boston Herald reported, citing a confidential medical school report on the incident. Cameron confirmed the accuracy of the Herald’s report.

Five of the researchers were released from the hospital the same day. One was held overnight, the Herald said. The six are now believed to be fine, Cameron said. He said the toxicology report was only recently completed.

“They were able to boil it down to a common denominator, the coffee pot, that very day, and the coffee pot was immediately taken away,” Cameron said.

Sodium azide is “a rapidly acting, potentially deadly chemical that exists as an odorless white solid,” according to the U.S. Centers for Disease Control and Prevention in Atlanta, and when mixed with water, it changes rapidly to a toxic gas.

Little Warning

“The odor of the gas may not be sharp enough, however, to give people sufficient warning of the danger,” the CDC noted.

Used commercially to swiftly inflate car air bags, sodium azide is commonly used as a preservative in biomedical research, Cameron said.

He said Harvard police are now investigating the incident, and so far have not announced any suspects, or even a motive in the case.

The coffee maker was located on a floor where basic research on immune systems is conducted, some of it on mice, Cameron said.

To contact the reporter on this story: Peter S. Green in New York at psgreen@bloomberg.net.

Last Updated: October 26, 2009 14:46 EDT