Dana White, the Ultimate Fighting Championship president, has insisted that his plans for a 12-fight mixed martial arts showcase this month will be safer for participants than staying at home or going to the grocery store during the coronavirus pandemic.

But with the showcase, U.F.C. 249, just 10 days away, it was unclear how White and the U.F.C. could ensure the safety of an entertainment venture that, unlike a grocery store, is not essential.

The closest major hospital, which could be needed if fighters get hurt, is a 40-minute drive away, and a hospital spokeswoman said her employers had not heard a word from the U.F.C. as of Wednesday. The Native American tribe that is providing the site — a casino that was shuttered because of the virus — has previously sought help with fights from California state referees, judges and other officials, but the U.F.C. is on its own now as it evades regulators who have told it not to proceed.

And while the U.F.C. has insisted on pressing forward — despite additional objections from combat-sports doctors and public health officials — some legal experts believe that county and state officials could step in, even though the April 18 event is being staged on sovereign tribal land.