Five people were found dead in a Richmond apartment Saturday afternoon, the Cache County Sheriff’s Office said.

Neighbors entered the unit in a triplex on the 300 block of Main Street after carbon monoxide detectors had been going off for an extended period, the sheriff’s office said in a news release. In the garage, they found a 43-year-old man dead.

Deputies responded about 12:15 p.m. and, after entering the apartment, found four more people dead in different areas throughout the unit, Sheriff Chad Jensen said. They were two boys, ages 16 and 11, and two girls, ages 12 and 5.

The two adjoining apartments were evacuated, according to the news release, and another adult man was taken to a nearby hospital for possible carbon monoxide exposure.

The cause of the deaths is under investigation, Jensen said.