Media playback is unsupported on your device Media caption Family and friends mourn those lost in California dive-boat fire.

The crew of the boat destroyed by a fire off California's coast were all asleep when the blaze started, US officials say.

Under federal law the Conception scuba boat should have had a crew member acting as a "night watchman".

The US National Transportation Safety Board (NTSB) has released a preliminary report into the 2 September fire.

All 33 passengers and a crew member sleeping below deck died in the blaze. Five crew members managed to escape.

The fire's cause is yet to be determined, but the NTSB say initial interviews with some of the crew revealed no reports of mechanical or electrical problems on the boat.

The 75-foot-long (23m) scuba-diving boat Conception was anchored metres off Santa Cruz Island, about 90 miles (145km) west of Los Angeles when it caught fire.

Image copyright EPA/SANTA BARBARA COUNTY FIRE HANDOUT Image caption The boat was totally engulfed in flames as crews tried to rescue those onboard

Rescue crew recovered the body of the last victim from the water on Monday, police said. Authorities believe all died of smoke inhalation.

"DNA testing is still being conducted to confirm identities of 7 of the 34 victims recovered," Santa Barbara County Sheriff's Office said on Twitter.

What does the report say?

The boat, owned and operated by Truth Aquatics Inc, was on a three-day diving trip to the Channel Islands but on the last night of the voyage, in weather conditions of minimal wind with patchy fog, the boat caught fire.

Coast Guard services received a distress call from the vessel at 03:14 local time (10:14 GMT).

Image copyright Getty/Ventura Country Fire Department Image caption Firefighters were unable to board the vessel to put the fire out as flames has already taken hold

The NTSB say at the time of the fire, the five crew members who survived were asleep in different areas of the three-level wood and fibreglass boat.

One of the crew members "was awakened by a noise and got up to investigate" when he "saw a fire at the aft end of the sun deck, rising up from the salon compartment below".

The crew member alerted his colleagues and they jumped down to the main deck to try to reach the passengers sleeping below in the main salon - with one crew member breaking their leg in the process.

However with their path blocked by fire and smoke, the crew jumped overboard and two members swam to the other end of the boat and reboarded.

Media playback is unsupported on your device Media caption Watch Santa Barbara residents respond to "terrible" boat fire

They "opened the hatch to the engine room, and saw no fire" and still unable to reach the passenger quarters they launched a small skiff and picked up the remaining crew from the water and transferred to a boat anchored nearby.

The captain carried on radioing for help while two crew members again returned to the vessel to search for survivors around the burning hull. The vessel burned to the waterline and sank.

Salvage operations to bring the wreckage to the surface for examination and documentation have begun and the NTSB said efforts were still going on to determine the cause of the fire.

The US Coast Guard has issued a new emergency safety recommendations following the deadly disaster.

Who was on board the Conception?

The names of five more victims were released on Tuesday afternoon, bringing the total number of identified victims to 27.

The five victims were identified as Adrian Dahood-Fritz, 40, from Sacramento; Lisa Fiedler, 52, from Mill Valley; Kristina "Kristy" Finstad, 41, from Tamrick Pines; Fernisa Sison, 57, from Stockton; Kristian Takvam, 34, from San Francisco.

The names of the remaining victims are expected to be released later this week.

Image copyright Getty Images Image caption People have left flowers at the dock where the Conception is based

Family members and friends of victims have been paying tribute to their loved ones.

Fiedler, who worked as a hairstylist, was described as a "kind-hearted" lover of music, nature and travelling with a "magnificent spirit".

"Everybody loved her. She was a kind, gentle person. She was a naturalist, she loved nature," Fiedler's mother Nancy told ABC7 News.