A test rocket owned by billionaire Jeff Bezos exploded Thursday night in Florida. The rocket, New Glenn, was built by Bezos’s space company, Blue Origin. The explosion happened at Cape Canaveral as workers were testing the rocket’s engines in preparation for a future launch.

Amazon’s internet satellites were supposed to ride on the New Glenn rocket. The satellites are part of a project to rival Elon Musk’s Starlink satellite internet service. The satellites themselves were not destroyed, as they were not on the rocket when it exploded.

Blue Origin called the accident an “anomaly,” meaning something unexpected went wrong. The cause of the blast is now being investigated by experts, the company said. The U.S. Federal Aviation Administration (FAA) is expected to assist in the investigation. Early reports say the launch pad may have also been seriously damaged.

It’s a further challenge for Blue Origin as it tries to catch up with Elon Musk’s space company SpaceX. The New Glenn rocket program has already experienced obstacles and technical problems over the last few years. Some recent missions also had trouble getting into the right orbit in space.

The accident could slow down Blue Origin’s plans. NASA recently awarded the company contracts related to future Moon missions under the Artemis program. The New Glenn rocket is expected to assist in carrying satellites and equipment into space for those missions

Following the explosion, Jeff Bezos posted a message online saying it was a tough day for the company. But he said Blue Origin will learn from its failure, rebuild, and continue working toward future launches.