Three people were found dead Monday morning inside a back apartment unit on Balboa Island, the Newport Beach Police Department said.

Police received a call at about 8:23 a.m. requesting medical aid in the area of Diamond Avenue and Bay Front Alley South, according to Heather Rangel, a Newport Beach police spokesperson.

Responding officers arrived and discovered two women and one man dead inside a room at the rental unit, police said.

Another man was also found at the apartment, and he was transported to Hoag Hospital with unknown injuries, police said. As of Monday evening, the man was listed in stable condition and is expected to survive.

“One of the people who called us is the person that was inside the residence,” Lt. Keith Krallman with NBPD told KTLA.

Authorities have not identified them publicly, but Krallman said they were all either friends or family members and were estimated to be in their 30s to 50 years old.

It is unclear what caused the deaths, and the circumstances of how the victims were discovered were unknown. Police said the coroner’s office is working to determine the manner and cause of the deaths, while investigators were exploring all possibilities.

“That is one possibility, that there was a possible drug overdose. But that has not been confirmed just yet,” Krallman said.

Orange County hazmat crews were also seen assisting authorities at the scene Monday afternoon.

“Any time there is a suspicion of any type of a possible drug overdose or the drug fentanyl possibly being present at a crime scene, a Hazmat unit will come out and assess and decontaminate so our officers can go in safely,” Krallman said.

No arrests were made.

Authorities were still in the early stages of the investigation and have received a search warrant to go back inside the home.

Officials said there was no threat to the Newport Beach community.