MyPillow CEO Mike Lindell said his website, Frank Speech, was hacked Tuesday morning, interrupting the livestream of his Cyber Symposium on how Chinese hackers defrauded the 2020 presidential election and delaying the start of the three-day event.

Mr. Lindell says he has 37 terabytes of “irrefutable” evidence that hackers, who he said were backed by China, broke into election systems and switched votes in favor of President Biden, which he plans to present at the event.

“We’ve been attacked, they attacked,” Mr. Lindell told the in-person attendees in Sioux Falls, South Dakota. “We have backup. We’re going to be up and running. But I’m going to wait to run that live[stream] to start because everyone’s gonna see everything we got.”

Mr. Lindell did not say who was responsible for the hack.

The livestream was restored just before 10 a.m. Central Daylight Time, one hour after the event was scheduled to begin.

The three-day event marks a culmination of Mr. Lindell’s highly publicized claims of election fraud, which have been widely discredited and cost him significantly both financially and in terms of reputation.

Once the livestream was restored, the event began with an opening prayer.

The full duration of the symposium is scheduled to be live-streamed on Mr. Lindell’s website, which he said he hoped would attract 1 billion viewers.

“It’ll be the most-seen event in history,” he told The Washington Times. “I believe that because everyone in the world is going to be curious and to see this. And they’re going to be talking going, ‘You got to see this. This is real. The United States was, their election was taken, hacked into by China.’”