BOSTON -- Harvard University Medical School will increase security and install new video cameras at its laboratories this week as police work to determine whether six people were intentionally poisoned at a research building.

The scientists and students fell ill on Aug. 26 after consuming a potentially lethal chemical that was present in their coffee, according to an internal memo sent to medical school students on Friday.

All six people had used a single-serve coffee machine near their pathology lab at Harvard’s New Research Building to prepare the coffee, and all later reported dizziness and low blood pressure.

Testing revealed the presence of sodium azide, a common preservative, in the coffee, the memo said. Sodium azide is an odorless white solid, according to the Centers for Disease Control Web site.

One person became unconscious. All six were taken to Beth Israel Deaconess Medical Center for treatment. None suffered long-term consequences from the poisoning.

The university said it does not know if the poisoning was deliberate or accidental.

“While we do not yet know how the incident occurred, we have recently learned that sodium azide ... was present in the coffee consumed by the six employees,” the memo reads.

Many workers and students who frequent the building said they had not yet heard about the incident.

"I'm actually kind of surprised," one said.

Swallowing the chemical can cause rapid breathing, dizziness and nausea, according to the CDC.

The federal Occupational Safety and Health Administration and the Boston Public Health Commission are investigating.

“We are in the process of installing additional security cameras throughout our buildings, and we are strengthening the security systems that manage access to the laboratories during both normal business hours and off hours,” the Harvard memo said.