Footage showed the New Glenn igniting on the pad at about 9pm ET (9am local time) before erupting into a massive fireball that billowed skyward, sending a towering plume of flames and smoke into the air.

Blue Origin said it had experienced an “anomaly”, a term commonly used by rocket companies to describe a launch failure or explosion.

“We experienced an anomaly during today’s hotfire test. All personnel have been accounted for. We will provide updates as we learn more,” the company said in a post on X.

A hot-fire test is where a rocket engine is fired up while anchored to the ground.

In a separate X post, Bezos said it was “too early to know the root cause” of the incident.

“Very rough day, but we’ll rebuild whatever needs rebuilding and get back to flying. It’s worth it,” he said.

Blue Origin said on Wednesday it was preparing the New Glenn rocket to launch 48 Amazon Leo satellites into low-Earth orbit, part of efforts to build a broadband constellation to rival Musk’s Starlink network. It did not provide a launch date.

Blue Origin has spent billions of dollars and roughly a decade developing New Glenn, a rocket 29-stories high with a reusable first stage meant to compete with SpaceX’s Falcon fleet and its more powerful Starship.

Musk responded on X to a video of the New Glenn explosion, saying: “Most unfortunate. Rockets are hard.”

The Federal Aviation Administration did not immediately respond to a Reuters request for comment.