SANTA BARBARA, Calif. — The boat had long operated with a modern fire-suppression system in its engine room and was deemed safe to sail, having passed a Coast Guard inspection as recently as February that required smoke detectors and fire extinguishers.

But that apparently was not enough to stop the brutal fire that overtook the Conception in the early morning hours of Labor Day, leaving 34 people dead and prompting increased scrutiny about whether regulations in place to prevent such tragedies go far enough.

Though the cause of the fire is unknown, the scope of Monday’s devastation has left industry experts and officials baffled at how a respected boat operator lost an entire excursion of people inside the hull of a ship outfitted with safety systems intended to protect any such vessel.

The deadly fire near the Channel Islands, a national park on the California coast, was the state’s worst maritime disaster in recent memory, and officials on Tuesday said they had called off a search for survivors.