An apparent accident at a dairy in a rural farming community in Colorado involving exposure to gas killed six people, including a high school student, authorities said Thursday.

Investigators are looking into what kind of gases may have played a role in the deaths Wednesday at Prospect Valley Dairy in Keenesburg, about 35 miles northeast of Denver. Crews recovered the bodies in a confined space at the dairy, the Southeast Weld Fire Protection District said.

“We are investigating these deaths as the possible consequence of gas exposure in a confined space,” said Jolene Weiner, chief deputy coroner for Weld County.

The identities of those who died, all Hispanic males, were being withheld pending notification of the families, Weiner said. A local school district said a high school student was among those who died.

Weld County Sheriff’s Office spokesperson Melissa Chesmore said her agency didn’t find anything indicating a crime took place.

“It looks like an accident,” she said, declining to elaborate or say where exactly the bodies were found, referring questions to occupational safety regulators.

Chauntra Rideaux, a U.S. Department of Labor spokesperson, said in an email that the Occupational Safety and Health Administration was investigating. The farm is a member of the Dairy Farmers of America, the group said.