AUSTIN, Texas (AP) — The recent blackouts that left 4 million Texas customers without electricity and heat during a deadly winter freeze also unplugged plants that could have generated more power, which was urgently needed as the state’s grid reached the breaking point, the head of a major energy corporation said Thursday.

Curtis Morgan, the CEO of Vistra Corp., told lawmakers at the outset of a public hearing on one of the worst blackouts in U.S. history that when officials from his company called utility providers, they were told they weren’t a priority.

“How can a power plant be at the bottom of the list of priorities?” Morgan said.

“You-know-what hit the fan, and everybody’s going, ‘You’re turning off my power plant?'” he said.

At least 40 people in Texas died as a result of the storm, and 10 days after the blackout started, more than 1 million people in the state were still under boil-water notices.

Lawmakers’ outrage fell heavily on the Electric Reliability Council of Texas, which manages the state’s grid. ERCOT has claimed that the scale of the forced blackouts — the largest in Texas history — averted an even more catastrophic failure that would have wiped out power to most of the state’s 30 million residents for months.

“Obviously what you did didn’t work,” said Democratic state Sen. John Whitmire of Houston, which had more than 1 million outages.

“It worked from keeping us (from) going into a blackout that we’d still be in today, that’s why we did it,” ERCOT president Bill Magness said. “Now it didn’t work for people’s lives, but it worked to preserve the integrity of the system.”

Among Vistra’s subsidiaries is, Luminant, which operates nearly two dozen plants across Texas. Morgan blamed outdated lists of critical infrastructure in Texas for darkening gas processers and production sites as grid managers began shutting off parts of the system.

Morgan didn’t say how many of the company’s plants were turned off or for how long, but he did say the company was within three minutes of power going offline at one nuclear plant, and that the main power grid in America’s energy capital was just moments away from total collapse Feb. 15.

“We came dangerously close to losing the entire electric system,” Morgan said.

Of Texas’ power generators that were not operational during the storm, Magness said the freeze was responsible 42% of the failures. A lack of fuel and equipment damage unrelated to the weather also contributed, but Magness said that for 38% of the plant outages, the problem remains unclear.

The outages lasted days for millions of Texas homes, and millions more lost water as water treatment plants shutdown and miles of pipes burst across the state. The toll of the storm included at least 15 hypothermia-related deaths around Houston, said Democratic state Rep. Ana Hernandez, vice chairwoman of the House State Affairs committee.