LEWISTON — The investigation continued Thursday into the death of Louis St. Pierre, a 60-year-old landlord who died following a fight at a Lisbon Street apartment house the day before.

The question for police is whether the fight caused St. Pierre’s death or if he collapsed as a result of pre-existing heart problems — he had recently undergone heart surgery, police said.

Investigators said the fight started in a hallway at 738 Lisbon St. and moved outside. One man who lives in the area said St. Pierre had jumped between two men who were fighting, one a tenant, the other a visitor.

Punches were thrown, police said, but detectives were still trying to pin down who threw those punches and who was hit. St. Pierre collapsed in a driveway, police said. His family rushed him to Central Maine Medical Center, where he later died.

St. Pierre, along with his wife, Janet, owned the apartment house, according to city records. The couple had lived in the building since 1993. Janet died in February. Together, the couple had a son, a daughter and several grandchildren.

An autopsy began Thursday. Lewiston police Lt. Michael McGonagle said they expect to have some results Friday.

The investigation involved more than a half dozen witnesses or potential witnesses, including other tenants of the building and their guests. By late Friday, no charges had been filed.