According to a summary of the findings, China’s preliminary report into what caused a China Eastern Airlines Boeing 737-800 to crash into a mountain last month, killing all 132 people on board, provides few new clues to help solve the mystery surrounding the country’s worst air disaster in nearly three decades.

The Civil Aviation Administration of China said in a statement Wednesday summarizing its findings that no problems were found in the maintenance records or flying conditions at the time of the disaster. Within 30 days of the March 21 crash, CAAC is required to submit a preliminary report to the International Civil Aviation Organization and all parties involved, including the United States, where the Boeing was manufactured.

Investigators are now concentrating on piecing together evidence to explain why the jet sped toward the ground before disintegrating on impact, with a last recorded speed of 1,010 kilometers per hour (628 miles per hour). The CAAC stated that it had found no anomalies in the flight’s operation prior to the crash.

According to the statement, data from the plane’s severely damaged flight recorders, also known as black boxes, is still being recovered and analyzed. The National Transportation Safety Board, a federal agency that investigates transportation accidents and is involved in the investigation, has aided in the retrieval of data from the two recorders in its Washington, D.C. lab.

The preliminary report has not been made public, according to the CAAC, because it contains no analysis or conclusion about the cause of the crash. According to ICAO rules, China has the option of keeping the information private, though countries are encouraged to publish a final report within 12 months of a crash.

According to the statement, the Boeing jetliner had been approved to fly and its flight crew was qualified. Before radar warned of a deviation in the plane’s cruising altitude at 2:20 p.m., just four minutes after the last exchange with ground control, radio communications between the pilots and air traffic controllers on the flight from Kunming to the southern metropolis of Guangzhou had been normal.

The jet was immediately hailed by air traffic controllers, but no response was received, according to the report. The engines, horizontal and vertical stabilizers, the rudder, and the cockpit were among the wreckage discovered at the crash site. According to the summary, a section of the right winglet was discovered about 12 kilometers from the crash site. According to the report, the impact formed a 45-square-meter (484-square-foot) pit that was nearly three meters deep.

China Eastern announced earlier this week that flights of the Boeing 737-800 model plane involved in the crash had resumed. They were forced to stay on the ground for nearly a month in order to conduct tests and analyze data related to their airworthiness. The airline stated that it was still conducting maintenance assessments. The 737-800’s return to service, according to aviation experts, suggests that the immediate or known issues surrounding the crash may not be with the plane.

The ICAO and Boeing did not immediately respond to a request for comment on whether they had received the report, which was not stated in the Chinese statement. The report has been received by the NTSB.

In early April, the NTSB dispatched a team to China to assist with the investigation, following strict protocols to avoid quarantine and begin working immediately. In late March, the agency tweeted that its team would not release any information about the investigation because it was under the authority of the Chinese government.