(Bloomberg) -- Elon Musk’s Space Exploration Technologies Corp. violated the terms of its federal license for a December test launch of its Starship spacecraft, a flight that ended in a fireball, according to a report.

It was unclear what part of the test violated the license, the Verge website said Friday in its article, which cited anonymous sources. A mishap investigation by the U.S. Federal Aviation Administration focused on SpaceX’s refusal to adhere to what the regulator authorized, a person familiar with the matter told Bloomberg News, confirming the Verge’s report. The person, who wasn’t allowed to discuss the matter, asked for anonymity.

SpaceX didn’t immediately reply to a request for comment made after regular business hours on Friday.

Stepped-up regulatory scrutiny played a role in delaying a test of the SpaceX’s Starship SN-9 prototype this week, the Verge reported. Musk expressed his frustration in a tweet on Thursday, slamming the FAA for “a fundamentally broken regulatory structure.” The agency said Friday that it would “evaluate additional information” from SpaceX as the company seeks to modify its launch license.

The rocket company had been touting the launch of the SN-9.

The Starship SN-8 flew on Dec. 9 with a successful ascent and a landing flip maneuver, remaining stable throughout the nearly seven-minute flight. But low pressure in a fuel tank caused the spacecraft to land too rapidly, resulting in a fireball at touchdown.

“While we recognize the importance of moving quickly to foster growth and innovation in commercial space, the FAA will not compromise its responsibility to protect public safety,” the FAA said in response to inquiries about the delay of the SN-9 launch. “We will approve the modification only after we are satisfied that SpaceX has taken the necessary steps to comply with regulatory requirements.”

SpaceX’s stainless steel Starship is designed to be a versatile, fully reusable craft that can carry 100 metric tons for deep space missions to the moon and Mars and also serve as a hypersonic, point-to-point vehicle to reduce travel times across Earth.

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