HYANNIS — Six people were injured, three of them seriously, when a high-speed ferry crashed into a jetty at the entrance to Hyannis Harbor Friday night, authorities said.
The Iyanough ferry was carrying 48 passengers, six crew members, and three food service workers from Nantucket to Hyannis when it struck the jetty and grounded on the rocks about 9:30 p.m, according to a statement from the Steamship Authority, which operates the vessel.
The rescue effort continued into early Saturday morning as the US Coast Guard attempted to retrieve passengers.
One seriously injured passenger was airlifted off the stranded vessel, and then flown by helicopter to a hospital for treatment of undisclosed injuries, said Hyannis Fire Capt. Thomas Kenney.
Other injured passengers were treated onboard the ferry by paramedics and rescue crews that were able to reach the ferry, Kenney said.
But several other passengers had to be airlifted off the vessel when sea and air conditions made it too difficult for crews to reach the Iyanough, he added.
At the time of the crash, three-foot seas were reported in Nantucket Sound, with winds gusting to 15 to 30 miles per hour, according to the National Weather Service in Taunton.
Multiple agencies from Cape Cod raced to the scene after the vessel sounded a mayday call just after 9:30 p.m., according to Kenney.
“It was a mayday, radio mayday, that was intercepted by our fire alarm office,” he said.
Kenney said he immediately notified the Coast Guard. Hyannis fire and police responded by ground and water, he added.
The first passengers to disembark by boat, rather than helicopter, made it to the pier at the Hyannis Port Yacht Club by 1:45 a.m.
They were quickly ushered onto an awaiting shuttle. One passenger was transported by stretcher to a nearby ambulance. Some were still carrying their life jackets.
Helicopters circled the ferry and nearby rescue vehicles, parked on what otherwise would have been a quiet street by the Hyannis Port Yacht Club.
Wayne Lamson, general manager of the Steamship Authority, offered thanks to the Coast Guard, the helicopter crew, and local rescue workers, in a statement early Saturday morning.
“Our concerns, first and foremost, are the safety and well-being of our passengers, and we deeply appreciate the efforts of all who guided them safely to shore,” Lamson said.
Police blocked off the pier to the public, but onlookers gathered at the scene to get a glimpse of the ferry that apparently veered off course.
“Nothing like this has ever happened,” said Pamela Stein, whose family has had a home on Irving Avenue across from the jetty for 45 years. “They (the ferries) go all winter and you just assume the captains are really experienced.”
Stein said she came to see the commotion after the helicopters woke her up. She was carrying binoculars, hoping like the passers-by all night, to sneak a glimpse of the marooned ferry.
Stein said she was shocked a ferry route that’s so routine could run so off course.
“I’ve been in worse storms,” she said. “If must have been really extreme for this to happen.”
The jetty, a giant pile of rocks extending several feet into the harbor, is near the Kennedy compound in Hyannisport, Kenney said.
“If you were standing on the . . . Kennedys’ front lawn, it would be right in front of you,” Kenney said. “The boat drove up on that pile of rocks.”
Kenney, a 36-year veteran of the Hyannis Fire Department, said he could not remember a time when a ferry had struck the massive jetty.
“I’ve had smaller boats hit that, maybe 15- to 25-foot-range boats, but this is the largest boat that’s ever hit it in my career,” he said.
On its website, the Steamship Authority describes the Iyanough as a 154-foot, high-speed ferry that travels from Nantucket to Hyannis in an hour. It carries up to 400 people. The authority said the Iyanough would be out of service until repairs are made, with traditional ferries temporarily transporting passengers who have purchased tickest for the high-speed ferry.
The Coast Guard dispatched boats from stations in Woods Hole, Chatham, and Brant Point on Nantucket, and a crew from Air Station Cape Cod, the agency said.
Rescue crews were scheduled to work into Saturday morning to “oversee the safe transfer of all passengers and ferry crew,” the statement said.
The cause of the grounding is under investigation, according to the Coast Guard.
Globe correspondent Jeremy C. Fox contributed to this report. Sara Salinas can be reached at firstname.lastname@example.org. Jacob Geanous can be reached email@example.com. Rowan Walrath can be reached at firstname.lastname@example.org