BRISTOL, R.I. (WPRI) ─ An external review by the Broad Institute is underway into the protocols of a lab at Roger Williams University after several people tested positive for COVID-19.

The Marine and Natural Sciences building on campus has been temporarily closed after 20 people who either worked or studied inside the building tested positive more than a week ago.

In a letter to students, the university says they retested those 20 people days later and learned 14 of those follow-up tests came back negative. To date, RWU has a total of 16 active cases with a positivity rate under 1%.

The cluster of cases was traced back to that specific building where there is a lab that uses non-viral materials that mimics the coronavirus for research.

A spokesperson for the university tells 12 News that at no point were the researchers in the lab using the actual COVID-19 virus during their research.

The spokesperson said there is “no way to distinguish if these cases were truly a positive of if the potential presence of lab material caused a positive result.”

The university said it discovered the cluster of cases through its mandatory testing protocol.

Dan Egan, president of the AICU Rhode Island, tells 12 News testing is a key factor in keeping the virus under control at colleges and universities.

“What institutions do is they use testing as its first line of defense,” Egan said. “Then, there are a number of quarantine and isolation steps in place developed in concert with the Department of Health that institutions will implement.”

Even though more than half of the follow-up tests came back negative, the university said everyone in the cluster of cases must continue to isolate, per Health Department protocols.