As a Lion Air jet began its ascent after taking off from Indonesia's capital last month, the plane's pilots fought to maintain control as an automatic safety system repeatedly forced the aircraft's nose down, investigators said Wednesday -- adding the plane should not have even been in service.

The new 737 MAX 8 faced struggles immediately during takeoff from Jakarta on Oct. 28 that may have overwhelmed the pilots, according to black box data revealed in the Indonesia National Transportation Safety Commission's report.

Investigators told reporters at a news conference they were still struggling to understand why the plane crashed into the Java Sea, killing all 189 people aboard. But officials cited multiple factors centered on faulty sensors and an automatic safety system that repeatedly forced the plane's nose down despite the pilots' efforts to correct the problem.

The head of the committee, Nurcahyo Utomo, said that problems experienced on a flight the night before from Denpasar in Bali to Jakarta should have kept the aircraft grounded.

"In our opinion, the plane was no longer airworthy and it should not have continued," he told reporters.

The MAX aircraft that crashed is the latest version of Boeing's popular 737 jetliner. Its new automated system pushes the nose down if a sensor detects that the nose is pointed so high the plane could go into an aerodynamic stall.

Pilots who flew the aircraft before the crash told investigators that the anti-stall system engaged due to erroneous airspeed and altitude indicators, but the flight crew managed to adjust the plane's pitch manually by shutting the automated system off. They were able to complete the flight and land the plane safely.

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Utomo added that it was "too early to conclude" whether the automated anti-stall system had contributed to the crash.

Authorities have recovered the flight data recorder but are still looking for the other black box, the cockpit voice recorder, which should reveal what else happened before the accident, according to Sky News.

In a statement following the release of the report, Boeing played up the possibility of pilot error, saying the aircraft the company manufactured was sound.

"As our customers and their passengers continue to fly the 737 MAX to hundreds of destinations around the world every day, they have our assurance that the 737 MAX is as safe as any airplane that has ever flown the skies," it said.

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The aircraft manufacturer noted that the investigators' report cited actions by the flight crew that led to the crash. Boeing also pointed to maintenance work and procedures that had failed to fix the aircraft's repeated problems.

The Indonesian investigation is continuing with help from U.S. regulators and Boeing.

More than 200 MAX jets have been delivered to airlines around the world. Earlier this month, pilots at American Airlines and Southwest Airlines complained that they had not been given all information about the new automated anti-stall safety system on the MAX.

The Associated Press contributed to this report.