A man and woman are dead after a vehicle plunged into Hamilton Harbour at the edge of Lake Ontario on Tuesday, police say.

Halton police confirmed early Wednesday a man, 55, and woman, 51, were found in the car pulled from the water overnight.

Police confirmed to CBC News that the couple were married.

Both of the deceased were from Burlington.

Police believe the man and woman found in the car were a married couple. (David Ritchie/CBC)

Emergency crews were called just after 8 p.m. ET Tuesday for reports that a car had driven into Hamilton Harbour from LaSalle Park.

Witnesses reported seeing a vehicle go through a concrete barrier and into the water at the marina, which is near Plains Road East and Waterdown Road.

The car was "fully submerged," police said, about 12 metres from the shore.

Witnesses and emergency services were unable to rescue the people trapped inside, and the car was pulled from the lake by divers and a heavy tow service.

Trevor Wadham heard two crashes and a splash, then watched as the car went down in the water.

He said he saw two bystanders jump in and try to help.

"People were kind of frantic to see what they could do," said Wadham, noting the speed of the car and the poor visibility in the lake.

"Really there was nothing anybody could do."

Tragically 2 middle aged adults were located inside the vehicle. One male and one female. Both residents of Burlington. Police are not searching for any other victims. ^ra —@HaltonPolice

An underwater search and rescue team from neighbouring Peel Regional Police was brought in to aid in the recovery efforts, as well as Toronto police divers.

The car was described as a navy blue sedan.

Visibility in the lake was poor during the rescue mission, said Elms, calling it an "exhaustive investigation" with emergency crews from several regions and units.

The investigation is ongoing.

Detectives will be exploring whether the driver of the vehicle experienced a medical episode which caused the crash.

Witnesses are asked to call Halton Police Service.