US investigators on Thursday sanctioned Boeing for revealing details of a probe into a 737 MAX midair blowout and said they would refer its conduct to the Justice Department, prompting the embattled planemaker to issue an apology.

The National Transportation Safety Board said Boeing had “blatantly violated” its rules by providing “non-public investigative information” and speculating about possible causes of the Jan. 5 Alaska Airlines door-plug emergency during a factory tour attended by dozens of journalists.

The decision sheds new light on strains between the crisis-hit planemaker and government agencies at a time when it is trying to avoid criminal charges being weighed by the Department of Justice ahead of a July 7 deadline.

“As a party to many NTSB investigations over the past decades, few entities know the rules better than Boeing,” the NTSB said.

The NTSB said Boeing would keep its status as a party to the investigation into the Jan. 5 Alaska Airlines emergency but would no longer see information produced during its probe into the accident, which involved the mid-air blowout of a door plug with four missing bolts.

Unlike other parties, Boeing will now not be allowed to ask questions of other participants at a hearing on August 6-7.

“We deeply regret that some of our comments, intended to make clear our responsibility in the accident and explain the actions we are taking, overstepped the NTSBs role as the source of investigative information,” Boeing said in a statement.

The NTSB’s criticism revolves around comments made during a media briefing about quality improvements on Tuesday at the 737 factory near Seattle — widely seen as part of an exercise to showcase greater transparency ahead of the Farnborough Airshow.

During the briefing, which was held on Tuesday under an embargo allowing contents to be published on Thursday, an executive said the plug had been opened on the assembly line without the correct paperwork to fix a quality issue with surrounding rivets, and that missing bolts were not replaced.

The team that came in and closed the plug was not responsible for reinstalling the bolts, Elizabeth Lund, Boeing’s senior vice president of quality, added.

The NTSB said that by providing investigative information and giving an analysis of information already released, Boeing had contravened its agreement with the agency.

“Boeing offered opinions and analysis on factors it suggested were causal to the accident,” it added.