(Bloomberg) -- Vistra Corp. said two units of Energy Transfer LP are threatening to cut off natural gas supplies to power generation facilities it owns in Texas because of a payment dispute over last year’s catastrophic winter storm. 

Vistra subsidiaries including Luminant Energy asked Texas oil and gas regulators to prevent Energy Transfer from terminating gas service to Luminant’s power plants, which serve about 400,000 Texas homes, according to a complaint filed with the Texas Railroad Commission on Wednesday. 

The “threat to terminate service in the middle of winter is illegal and grossly irresponsible and should be prohibited by this commission,” Vistra said in the complaint. 

Energy Transfer didn’t immediately respond to comment requests by phone and email.

The two units, Energy Transfer Fuel and Oasis Pipeline, are threatening to cease gas service by Jan. 24 because Vistra won’t pay $21.6 million in fees stemming from the February winter storm, when freezing temperatures knocked off gas supplies, contributing to widespread blackouts. The dispute comes as Texas is bracing for a new round of cold and sleet that will test the state’s power grid over the next several days. 

Vistra alleges in the filing that the fee is illegal and stems from the power generator securing and delivering gas into the pipeline operators’ systems during the storm.

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