Four members of Texas' power grid operator resigned from their posts Tuesday after a winter storm led millions of homes to lose power across the state last week, according to a public filing.

Why it matters: Their resignations come days after Texas' public utility commission launched a probe to discover the "factors that combined with the devastating winter weather to disrupt the flow of power," throughout the state.

Electric Reliability Council of Texas (ERCOT) Chair Sally Talberg resigned along with Vice Chair Peter Cramton and board members Raymond Hepper and Terry Bulger.

• During the storm, ERCOT, which manages the flow of electric power in the state and is separate from the federal power grid, began conducting power outages to balance the demand and supply of the grid.
• In the aftermath, wholesale power prices rose from roughly $50 per megawatt hour to $9,000, WFAA reports — noting some Texans faced bills of up to $17,000 so far this month.
• ERCOT said last week that the grid almost suffered a catastrophic failure that could have caused uncontrolled blackouts leaving residents without power for months.

The big picture:Texas Attorney General Ken Paxton formally demanded copies of communications and other documents from ERCOT and Texas power companies related to the winter storm, Axios' Ben Geman reports.

• Texas Gov. Greg Abbott (R) called for an investigation into ERCOT on Tuesday and called the expensive energy bills "unacceptable."