At least 33 people were feared dead after a boat caught fire off Santa Cruz Island, California, early Monday morning, officials have confirmed.

The Coast Guard said it responded after overhearing a Mayday call around 3:15 a.m. of an “engulfed 75-foot commercial diving vessel with 38 people aboard.”

Firefighters from two local fire departments were fighting the fire when the vessel sank 20 yards offshore in 64 feet of water, the Coast Guard said in a news release.

“Five people were evacuated aboard a good Samaritan pleasure craft Great Escape,” the release said.

“Currently, 33 people aboard the vessel are unaccounted for,” the release added.

Earlier. Fox affiliate KTTV confirmed with the Ventura County Fire Department that there were nearly three dozen fatalities. Lt. Cmdr Kroll later confirmed the ship sunk near the north shore of Santa Cruz Island after taking on water.

A tweet from VCFD said they responded to boat fire off the north side of Santa Cruz Island at approximately 3:28am.

A tweet from VCFD said they responded to boat fire off the north side of Santa Cruz Island at approximately 3:28am. (VCFD)

According to Coast Guard Lt. Cmdr Matthew Kroll those who had not been accounted for were sleeping below deck and those who had been rescued were crewmembers sleeping on top of the deck.

Local media reported that one of the crewmembers was the boat's captain

The boat was named the Conception and was anchored off Santa Cruz Island when it caught fire, Santa Barbara County fire officials said.

Shortly before 5 a.m. local time, the U.S. Coast Guard tweeted that it was coordinating a large rescue effort in response to the fire.

“The Coast Guard has launched multiple rescue assets along with assets from local agencies to assist more than 30 people in distress on a 75ft boat near Santa Cruz Island,” the tweet said.

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Another tweet an hour later said the vessel was reported as being on fire and that one of those rescued had minor injuries.

Firefighters with the Ventura County Fire Department responded around 3:28 a.m., according to a spokesperson.

The Coast Guard responded with two helicopters, two 45-foot Swift boats and an 87-foot cutter.

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Officer Nathan Alldredge of the Santa Barbara Harbor Patrol told Fox News that his office responded to a mutual aid call around 4 a.m. local time.

Multiple agencies responded after a commericial diving boat caught fire off Santa Cruz Island in California early Monday

Multiple agencies responded after a commericial diving boat caught fire off Santa Cruz Island in California early Monday (Santa Barbara County Fire Department)

Alldredge said the call was for the diving boat Conception which is based in Santa Barbara Harbor. The officer said the boat is a fully- equipped 75-foot commercial diving boat that takes out recreational scuba divers and is able to spend multiple days out at sea.

KKFX-TV reported that Conception's owner Glen Fritzler met with Coast Guard officials at the Channel Islands Harbor station Monday morning.

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Fire officials said the Conception based in Santa Barbara Harbor was anchored off Santa Cruz Island when it caught fire around 3:30 a.m. Monday. 

Fire officials said the Conception based in Santa Barbara Harbor was anchored off Santa Cruz Island when it caught fire around 3:30 a.m. Monday.  (Santa Barbara County Fire Department)

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Fritzler's Truth Aquatics website says the Conception has bunk space for 46 people and “rafts and jackets for 110 passengers.”

Truth Aquatics posted a photo of the Conception on its Facebook page five days ago with the caption, “there's just something about being on the water.”

Fox News' Lee Ross contributed to this story.