A UPS cargo plane was on the verge of taking off from Louisville, Kentucky, when a warning bell echoed through the cockpit. Over the next 25 seconds, the sound persisted as the pilots struggled to keep the aircraft under control. The plane had only just cleared the runway, its left wing engulfed in flames and missing an engine, when it crashed back to the ground in a blazing explosion, according to the chief investigator’s report on Friday.

The crash occurred on Tuesday at UPS Worldport, the company’s primary global aviation hub. Tragically, the accident claimed the lives of 13 individuals, including the three pilots aboard the MD-11 jet, which was en route to Honolulu.

Todd Inman, a member of the National Transportation Safety Board, revealed that the cockpit voice recorder captured the alarm sounding roughly 37 seconds after the pilots engaged takeoff thrust. Various alarms can indicate different issues, he explained, and while investigators have yet to determine the specific reason for this alert, they are aware that the left wing was ablaze and the engine on that side had separated from the aircraft.

Inman noted that it will take several months before a full transcript of the cockpit recordings is released to the public as part of the ongoing investigation.

Jeff Guzzetti, a former crash investigator for the federal government, suggested that the alarm was likely an indicator of the engine fire.

Investigators look to video for clues

Dramatic video captured the aircraft crashing into businesses and erupting in a fireball. Footage from phones, cars and security cameras has given investigators evidence of what happened from many different angles.

The NTSB clarified Friday that preliminary data on the aircraft’s altitude indicated it got only about 100 feet above ground level, not 475 feet. It reached a speed of 210 mph (340 kph) before crashing just outside the airport, Inman said.

The left engine’s main component and pieces of fan blades were recovered from the airfield. Inman said UPS indicated no maintenance work was performed just before the flight. He noted investigators will look at video to see what, if anything, was being done around the MD-11 aircraft in preceding days.

The UPS package handling facility in Louisville is the company’s largest. The hub employs more than 20,000 people in the region, handles 300 flights daily and sorts more than 400,000 packages an hour.

UPS Worldport operations resumed Wednesday night with its Next Day Air, or night sort, operation, spokesperson Jim Mayer said.

Lawsuit alleges negligence by UPS and others

Litigation over the crash has already begun. A federal lawsuit was filed Thursday against UPS by an automotive repair shop destroyed in the crash and a resident treated at a hospital after breathing in smoke.

The manufacturer of the plane and its engine also were named in the lawsuit, which alleges the defendants “negligently breached their duty of reasonable care and preventing unreasonable harm.” It seeks unspecified damages.

The companies named as defendants didn’t immediately return emails seeking comment Friday. ___

Mattise reported from Nashville. AP writer Ed White in Detroit contributed to this report.