US refiner Valero Energy Corp on Thursday warned of a bigger first-quarter loss compared to the previous three months due to higher costs related to the severe winter weather in Texas in February.

Freezing weather in US central and southern states in mid-February had led to power outages and gas-supply disruptions that knocked oil refineries and chemical plants out of commission for up to two weeks.

Valero said it expects net loss attributable to its stockholders in the range of $2.05 to $1.81 per share for the first quarter, compared with an 88 cents per share loss in the fourth quarter.

The estimated preliminary impact of excess energy costs to loss is $1.18 to $1.14 per share, Valero said, adding that the electricity and natural gas costs were incurred mainly by its refining and ethanol business segments.

Rival Phillip 66 also forecast a bigger-than-expected adjusted loss for the first quarter, citing the severe winter that battered its US Gulf Coast petrochemical operations.

Last week, Exxon Mobil said the winter weather would cut its first-quarter profit by up to $800 million, with the largest impact on its chemical and refining units.