Updated

Alon USA Energy Inc. says the Texas refinery that exploded Monday could be out of commission for two months.

President and CEO Jeff Morris says the refiner should have contingency supply plans in the coming days.

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The company doesn't know what caused the blast at the Big Spring, Texas, plant, but says it happened near a propylene splitter unit. The fire is now out and an investigation will begin soon.

All but one of the four workers hurt in Monday's explosion were released from the hospital Monday. The company says the fourth employee is being treated for burns and is thought to be in stable condition.