Nashville, TN — Authorities responding to a home in Tennessee found two people dead and two others unresponsive, officials said.

Crews also found a generator in the living room and “high levels of carbon monoxide” in the home, Nashville Fire Public Information Officer Kendra Loney told news outlets.

“While carbon monoxide was found, it is not clear if that is the cause of death,” Loney said.

The two unresponsive adults were taken to Vanderbilt University Medical Center in critical condition, she said.

Metro Nashville Police and the medical examiner are investigating the deaths.