PUNTO FIJO, Venezuela — Venezuelans who live next to the country's biggest oil refinery say they smelled a strong odor of sulfur hours before a gas leak ignited in an explosion that killed at least 39 people and injured more than 80.

The Amuay refinery was still burning on Sunday more than a day after the blast, sending up a thick column of black smoke.

Residents in a neighborhood next to the refinery say that starting about 7 p.m. on Friday they noticed the unusually strong odor. Government officials say the blast occurred about 1:15 a.m. on Saturday when the gas leak created a cloud that ignited.

The cause of the disaster is under investigation.