The passengers were all asleep below decks, according to the information the Coast Guard received.
A search was under way on Monday for 34 missing people in a pre-dawn fire that sank a commercial diving boat off a Southern California island, authorities said, and some local media outlets reported that some passengers were killed.
Five crew members were rescued by a "good Samaritan pleasure craft" after a distress call was reported at 3:15 a.m. local time as the 75-foot (23-metre) vessel burned about 20 yards (18 meters) off of Santa Cruz Island, the U.S. Coast Guard said in a statement.
"The crew was already awake and on the bridge and jumped off," Coast Guard Captain Monica Rochester told a news conference.
Some news outlets reported that a local fire department said several people were dead, but the Coast Guard has not confirmed any fatalities in the fire that engulfed the Conception, a pleasure craft used by scuba divers.
The passengers were all asleep below decks, according to the information the Coast Guard received, Rochester said.
James Kohl, brother of one of the missing passengers, told KTLA TV in Los Angeles he was told there was a propane gas explosion on board, but Rochester said she could not confirm that.
UNCERTAINTY OVER DEATHS
Ahead of the press conference, the Los Angeles Times reported that Ventura County Fire Department (VCFD) Captain Brian McGrath said there were some fatalities.
“We do have fatalities aboard, but we do not know the numbers here yet," McGrath told the Times in comments that came before the news conference.
During the news conference, however, Rochester and VCFD Deputy Chief Dustin Gardner did not confirm that anyone aboard had died.
Of the five persons rescued near the coast of Santa Barbara, at least one had minor injuries, the Coast Guard said.
An image posted by the VCFD shows the vessel engulfed in flames. It sank in 64 feet (20 metres) of water with just the tip of its bow showing, the Coast Guard said.
Local media reported foggy conditions along the southern California coast.
If there are fatalities, a coroner's inquest will be conducted by Santa Barbara officials, county Sheriff's Office spokesman Lieutenant Eric Rainey said by phone.
Rainey also said he could not confirm any fatalities but said he presumed there were some deaths because of "the extent of the fire and the fact that I think the rescued individuals told those rescuers that there were people on board that didn’t make it off the boat.”
"I’m crossing my fingers that there may be people on the shore," he added.