By Gary McWilliams

(Reuters) – Officials of Texas’ grid operator on Wednesday defended their handling of the state’s massive power outage, saying managers prevented a catastrophe while acknowledging the personal suffering during the extreme cold.

Directors of grid operator Electric Reliability Council of Texas (ERCOT) held their first meeting since winter storms that brought subfreezing temperatures for days, cutting power to up to 4.3 million people and causing millions of dollars of damages.

Six ERCOT directors have resigned and a board nominee declined a seat amid sharp criticism of their performance.

Sally Talberg, chairman of the board and one of the six to submit a resignation, said ERCOT “worked tirelessly” to keep the grid from collapse. She led Chief Executive Bill Magness through a sometimes hour-by-hour review of the loss of power available to the grid and communications with consumers and officials.

Texas has no mandatory weatherization standards for the power plants that supply the grid, Magness said, pointing to a likely direction for lawmakers as they begin hearings on the weather disaster on Thursday.

About 48% of the power generation available in the state was forced offline at the peak of the outages due to cold weather, lack of fuel or mechanical failures, Magness said. ERCOT had ample reserves available through Sunday, when generators began to drop off the grid.

Utilities cut power to homes and businesses to prevent serious damage to generators and transmission lines, he said. Plans to rotate outages among consumers could not happen because of the sizeable loss of generation, he said.

Randal Miller, who represented independent retail power providers, resigned late Tuesday, leaving the board with seven vacancies. Tanberg, ERCOT’s vice chairman and three other directors, all of whom live outside of Texas, also submitted resignations. Directors have been widely criticized for their handling of the outage and for not living in the state.

Texas Governor Greg Abbott earlier called for resignations. The state’s investigation will “uncover the full picture of what went wrong” and ensure it is not repeated, he said in a statement on Tuesday.

(Reporting by Gary McWilliams; Editing by Chizu Nomiyama, Steve Orlofsky and Jonathan Oatis)