Indianapolis police are investigating a concerning death that occurred at a Planet Fitness gym. 

Derek Sink was found dead in a tanning bed at the workout facility three days after he entered the building, the Marion County Coroner’s Office (MCCO) confirmed to People. He was 39.

“This remains an ongoing death investigation,” a MCCO spokesperson told the outlet. “The Marion County Coroner’s Office will determine the exact manner and cause of death.”

Sink had visited the Planet Fitness on Nov. 8 and his body was discovered the morning of Nov. 11, his family told local NBC affiliate WTHR. His aunt also told the news station that, due to him wearing an ankle monitor, investigators determined Sink never left the gym after his arrival.

Two days after going to the gym, Sink was reported missing by his family, according to police records obtained by Indianapolis Star. 

No cause of death has been determined in the case.

Elizabeth Len—a local woman who was visiting the Indianapolis Planet Fitness on the morning of Sink’s discovery—said she detected a bad smell after entering the building on Nov. 11 before realizing it was coming from the tanning beds.