State officials investigating a weekend boating accident in which two New York teens had to be rescued unconscious in waters off Jennings Beach say the probe could take as long as several months.

Investigation of the Sunday afternoon accident is being handled by authorities from the state Department of Energy and Environmental Protection, after local emergency personnel scrambled to help revive the girls and transport them to the hospital.

No charges had been filed as of Thursday.

The incident took place about 4:30 p.m. Sunday when two 13-year-old girls from Long Island, riding a tube towed by a dinghy, slammed into the side of a large New York-based yacht.

The girls, who had to be pulled unconscious from the water after the crash, were transferred Monday to the Yale-New Haven Hospital intensive-care from hospitals in Bridgeport.

The condition of both girls is improving, police said later. They were both in good spirits, police said, but don’t remember details of the accident.

One of the girls initially was in critical condition Sunday evening, while the other was less seriously injured, Police Chief Gary MacNamara had said.

The teens were rescued from the water by people aboard the yacht, police said, including the yacht’s owner, who is the father of one of the injured teens.

The Fairfield police marine unit was dispatched to the scene, where Marine Officer Keith Perham found the girls had been taken aboard the 69-foot-long yacht, “Tranquillo,” anchored about one-eighth of a mile off Jennings Beach.

Perham, joined by personnel from the Bridgeport police marine unit, boarded the yacht and found the two teenagers were still unconscious.

They stabilized the girls for transport to South Benson Marina, where firefighters and AMR paramedics were standing by.

The girls were riding a two-person tube being towed by a Nautica rubberized ribbed tender, which police said apparently was part of the yacht’s equipment.

Minutes into the ride, the towing dinghy appeared to lose control and the two teens aboard the tube struck the side of yacht. The impact threw both girls face down and unconscious into the water, police said.

The incident is similar to an accident last year when 16-year-old Emily Fedorko, of Greenwich, was killed and another girl seriously injured when they were run over by a boat that was towing them on a tube.

The accident prompted a new state law this year under which boat operators must be 16 years old and have a legal driver’s license.

“The quick actions of the private boaters that pulled the girls from the water and called 911 directly impacted the speed and effectiveness of medical care,” Assistant Fire Chief Scott Bisson said in a statement issued after the incident.

Police from the state Department of Energy and Environmental Protection turned investigation of the accident over to its Boating Accident Reconstruction Unit, assisted by Fairfield police.