Four workers at a Houston refinery were injured when a tank of sulfur caught fire and released fumes.

The leak was quickly contained Monday morning at the Valero Houston Refinery. Nearby residents were told they could go to a shelter to wait out the fumes.

Valero Energy Corp. spokesman Bill Day says four workers were taken to a hospital for evaluation.

The cause of the fire was not immediately determined.

The Valero refinery produces gasoline and gas derivatives.