Nine people remain missing after a UPS plane departing Louisville Muhammad Ali International Airport in Kentucky on Tuesday crashed, killing at least 12 people.

Dozens of federal aviation investigators are on the ground in Louisville searching the crash site's debris field, which covers nearly a half-mile area.

Investigators are reviewing 63 hours of data collected from the black box of a UPS cargo plane involved in a deadly crash that killed at least 13 people in Louisville, Kentucky, earlier this week. Nine people remain missing as authorities sift through the wreckage of Tuesday's crash in an attempt to piece together what went wrong.

The UPS cargo plane crew tried to control the aircraft for about 25 seconds before it crashed into a ball of flames shortly after taking off on Tuesday.

The cockpit voice recorder captured a persistent bell that began about 37 seconds after the crew called for takeoff thrust, and the bell continued until the recording ended, an NTSB official said.

As a bell sounded in the cockpit, three UPS pilots tried to control a cargo flight that crashed this week in Louisville, Kentucky, killing at least 13 people, the National Transportation Safety Board said on Friday.

Captain Richard Wartenberg, First Officer Lee Truitt and International Relief Officer Captain Dana Diamond were those on board the flight, according to UPS. Friday, a family shared that two of its members, Louisnes Fedon and his young granddaughter Kimberly, were also among those who died after the plane went down.

A UPS cargo plane crashed at a Louisville, Kentucky, airport where the company operates its largest package delivery hub. UPS calls the giant center Worldport.

The left engine came off a doomed United Parcel Service Inc. freighter moments before it crashed in a fireball near the company’s global hub in Kentucky, killing at least 12 people.Three crew members aboard the aircraft are believed to be among the casualties,