China’s aviation authority said on Wednesday the black boxes of a China Eastern Airlines Boeing 737-800 jet that crashed last month were “severely damaged” and it was still recovering and analyzing the data to help determine the cause.

In a statement regarding its preliminary report on the crash that killed 132 people, the Civil Aviation Administration of China (CAAC) did not make public any information from the flight data recorder and cockpit voice recorder that was sent to Washington for analysis.

CAAC said the flight crew were qualified, the jet was properly maintained and the weather was fine when flight MU5735, which was en route from Kunming to Guangzhou, plunged from cruising altitude and crashed in the mountains of Guangxi on March 21