Authorities have suspended the search for those still missing after a deadly fire engulfed and destroyed a dive-boat off the coast of California on Labor Day.

Thirty-four people are presumed dead, but only 20 bodies — eleven women and nine men — have been recovered. Divers have seen from four to six other bodies among the remains of the boat underwater, according to Santa Barbara County sheriff Bill Brown.

Five crew members who jumped off the boat and were rescued are the only known survivors among the 39 people who were aboard.

The 75-foot boat, the Conception, left from Santa Barbara’s Channel Islands Harbor on Saturday for a three-day scuba-diving trip. In the dead of the night early Monday, near Santa Cruz Island off the coast of California, the boat caught fire for reasons that remain unclear.

“This is probably the worst-case scenario you can possibly have,” said Brown. “You have a vessel that’s on the open sea, that is in the middle of the night. I mean, it’s 3:30 in the morning.”

Passengers are thought to have been asleep when the fire broke out. Ventura County firefighters reached the boat within 15 minutes, at which point it was already engulfed in flames.