MEXICO CITY — Firefighting crews extinguished a fire aboard a fuel tanker belonging to the Mexican state oil company, Pemex, late Sunday afternoon, about 30 hours after an explosion sent flames billowing into the air off the Gulf Coast port of Veracruz.

Pemex said all 31 crew members aboard the tanker, the Burgos, were safely evacuated.

The tanker was carrying 80,000 barrels of diesel fuel and 70,000 barrels of gasoline, but officials said the boat’s double hull reduced the risk of a spill.

“Up to now, we have not detected any extensive spill,” José Antonio González Anaya, Pemex’s chief executive, said at a news conference in Veracruz that was broadcast by radio on Sunday, shortly before the fire was contained.

It was too early to determine the cause of the explosion, he said.

The 558-foot Burgos was carrying the fuel from the port of Coatzacoalcos to Veracruz and was 6.7 nautical miles offshore when the explosion occurred at 11:30 a.m. on Saturday, Mexico’s communications ministry said.