OLYMPIA, Wash. (AP) — Authorities brought in outside experts on Wednesday to find the source of carbon monoxide believed to have killed one student and sickened two others at a college in Washington state.

The experts, from a forensic engineering firm that specializes in carbon monoxide investigations, were at the housing unit at The Evergreen State College in Olympia to conduct the analysis, Washington State Patrol spokesman Chris Loftis said.

A student residence manager called campus police Monday evening to report being unable to contact the students inside a modular home. An Evergreen police officer who broke down the door to help reach those inside was hospitalized overnight, according to police Chief David Brunckhurst.

The Thurston County Coroner’s Office identified the dead student as Jonathan Rodriguez, 21, of nearby DuPont. His autopsy was set for Thursday.

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Two students were also hospitalized. Evergreen spokesperson Farra Layne Hayes said Wednesday that she did not have further information about their conditions or if they had been released.

Earlier Monday, an alarm company contracted by the college responded to carbon monoxide alarms, Layne Hayes said. She said she did not have details about what that response entailed or whether the alarms came from the same modular housing unit where the student died.

Every residence on campus has a carbon monoxide detector, Layne Hayes said.

“This is a tragedy, and we grieve for our students and families,” Evergreen President John Carmichael said in a statement. “The safety of students, staff and faculty remain Evergreen’s top priority.”

Carbon monoxide is an odorless, colorless gas produced by the burning of fuels, including gas, wood, propane or charcoal. If not properly ventilated, appliances and engines can cause it to build up to dangerous levels.