WESTPORT — Detectives are investigating the possible cause of an accident Saturday night that sent a car plunging into the chilly Saugatuck River, leaving one passenger dead.

Police are considering the dark and rainy conditions and that the husband and wife in the car were from out of state and possibly lost, among possible contributing factors, Westport Police Lt. David Farrell said Wednesday morning. The department believes no foul play was involved, and the man, Richard Lamendola, died from drowning, the State Chief Medical Examiner’s Office said Monday.

The woman was rescued quickly through a joint firefighter, police and EMS effort after diners at the Whelk Restaurant on Riverside Avenue heard screams for help from the river. She told rescuers her male companion was still in the water. Lamendola, 76, of Syosset, N.Y., and his wife were in a car that plummeted into the river from a State Boat Launch off of Elaine Road in Westport around 7 p.m. on Feb. 25.

“I couldn’t be happier with the efforts of Fire, EMS and Police,” Police Chief Foti Koskinas said Wednesday morning. “We believe it happened during the downpour when very heavy rain was coming in, and it’s too early to determine what the exact circumstances were.”

Detectives are also examining the car’s GPS history, following up with the woman and processing evidence, Farrell added. Koskinas said the department still has a number of interviews to conduct.

“We want to learn if there was a way that it could have been prevented and to give the family some closure of why things happened the way they did,” Koskinas said.

After diners at the Whelk heard screams for help coming from the water and called police, who then contacted the fire department and joint dive team, rescue efforts began around 7:30 p.m. on Feb. 25. Fire Chief Robert Yost praised the “quick thinking” of the diners and rescue workers.

Yost on Tuesday called the woman’s rescue a “joint effort and operation” overseen by a unified police and fire command, along with EMS aid. Farrell said he was “truly proud” of the police, firefighters and EMS who responded Saturday.

Two emergency responders first to the scene boarded a civilian boat with keys on board and pulled the woman from the water. A firefighter acted “heroically,” Farrell said, swimming out in the cold water to get to the woman shortly before the boat could, an effort he believes may have saved her life.

She alerted the responders a man in the car with her was also in the cold river. A police officer spotted the man from the Bridge Street bridge, according to Yost. EMS gave the man, Lamendola, CPR and he was taken to Norwalk Hospital.

In the case of incidents involving a boat launch, like Saturday night’s tragedy, the state’s Department of Energy and Environmental Protection evaluates what happened to determine whether any factors contributed to an accident and discern if any safety changes need to be made, according to Connecticut DEEP Communications Director Dennis Schain.

He added on Tuesday that Westport Police’s final accident report will help the department with evaluating the State Boat Launch following Saturday’s incident.

Chris Marquette contributed reporting.