PONTE VEDRA BEACH, Fla. -- Alcohol was found on the boat that plowed into a tugboat and barge docked along the Intracoastal Waterway Sunday night, killing five people and injuring nine others, investigators said on Tuesday.

The National Transportation Safety Board and the Florida Fish and Wildlife Conservation Commission provided an update on their investigation of the fatal boat crash about one mile north of the Palm Valley Bridge.

Four Jacksonville-area residents and one person visiting from California died at the scene. Two of the nine people hospitalized after the accident remain in critical condition at Shands-Jacksonville Medical Center. Only one had been released as of Monday night.

FWC Capt. Gregg Eason verified alcohol was aboard the boat. Eason declined to say what kind of alcohol was found or whether the operator of the vessel had been drinking.

"We believe alcohol was on the boat because the first responders have told us that when they got there they saw alcoholic beverages on the vessel," Eason said. "That's not making any accusations that the operator was consuming alcohol. We don't know yet who was and was not consuming alcohol."

Unlike cars, it is not against the law to have open containers on a boat as long as the operator is not impaired.

The boat's owner, Melvin Bethel, of Ponte Vedra Beach, was among those hospitalized after the crash, but officials said they were still investigating whether he was at the controls when it slammed into the tug.

Five victims have been interviewed, but investigators have not said whether they know who was behind the wheel or how fast the boat was traveling.

Officials said the area near the Palm Valley Bridge is a no-wake zone, which boaters should pass through slowly. However, the owner of a restaurant on the ICW told Channel 4 he and a group of employees were sitting outside and saw the boat go by very fast.

"This boat was pretty close to full throttle as far as I'm concerned," said The Bridge Restaurant owner, John Cakmis.

He said it's not unusual to see boats speeding through the area but he knew something was wrong on Sunday when he heard emergency vehicles shortly after seeing the boat go by.

"I stood up and said, 'They need to slow down.' Approximately 20 minutes later, we started hearing emergency vehicles," Cakmis said.

Eason confirmed the boat was headed back to Jacksonville Beach after a group of 14 people had spent Sunday afternoon at the Conch House restaurant in St. Augustine Beach.

The FWC is conducting an investigation that could include criminal charges. They are also looking into the speed the boat was traveling, whether the 22-foot Crownline was carrying more than its capacity, and whether the tugboat was docked.

NTSB investigator Deborah A.P. Hersman said the agency doesn't investigate many boating accidents, but that the number of deaths and injuries met the agency's criteria for a serious accident that needed special attention. The NTSB's primary interest is to see what could be learned to prevent future accidents.