One man is dead and two more without life jackets are missing after high speed motorboat crash into a break wall in the mouth of the Connecticut River

One man has been found dead as two others with no life jackets remain missing after a boat crash at high speed on the Connecticut River.

The men in their mid to late 20s were aboard the single motorboat with six other people when it hit an east-facing jetty near Harbor One Marina in Old Saybrook, Connecticut. 

The high speed crash left the boat broken into pieces and all the passengers in the water, according to Joey Kellems from the US Coast Guard's Long Island Sound sector.

He told CNN that six people were rescued, while the three men, who weren't wearing life jackets, remained missing as the Coast Guard scoured the waters near the crash site on Monday night.

One of the men has since been found dead during the search, according to DEEP. 

The men in their mid to late 20s were aboard the single motorboat with six other people when it hit an east-facing jetty near Harbor One Marine in Old Saybrook, Connecticut (pictured in the background are search crews on the water following the crash)

Six people were rescued, while the three men, who weren't wearing life jackets, remained missing as the Coast Guard scoured the waters near the crash site on Monday night (pictured: general view of Harbour One Marina)

The incident happened when the boat crashed into an east-facing jetty near Harbor One Marina in Old Saybrook, Connecticut

The high speed crash left the boat broken into pieces and all the passengers in the water, according to Joey Kellems from the US Coast Guard's Long Island Sound sector (pictured: search and rescue teams in the Harbour)

The conditions of the six people rescued - one man and five women aged 24 to 30 - is unknown after they were transported to hospital. 

The search and rescue teams from the Coast Guard responded with air and water support as other aid agencies also participated in the search.

The crash has been declared a mass casualty incident and dive teams are on scene to find the missing men. 

The Coast Guard has not yet revealed how the boat crashed, but said it received the call about the incident at 9pm.

Old Saybrook is a coastal town about 30 miles away from New Haven, Connecticut.

The investigation into the boating crash is ongoing.