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A cockpit voice recorder recovered in the aftermath of the deadly crash of a Boeing 767 cargo jet that crashed in a marshland near Houston last month indicates a loss of control before the aircraft went down, the National Transportation Safety Board said Tuesday.

Three people were killed when the Atlas Air plane flown on behalf of online retailer Amazon crashed in Trinity Bay, east of Houston, on Feb. 23, according to the agency and Atlas Air. The plane was also carrying cargo for the U.S. Postal Service, the NTSB said.

The recovered voice recorder shows that "crew communications consistent with a loss of control of the aircraft began approximately 18 seconds prior to the end of the recording," according to the NTSB, which is investigating the crash.

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Pilot Ricky Blakely, 60, co-pilot First Officer Conrad Aska, 44, and jump seat rider Sean Archuleta, 36, were killed in the crash that was reported shortly before 12:45 p.m., authorities have said.

Archuleta was a captain and pilot with Mesa Airlines, and had been a pilot there since 2013, the airline has said.

The plane was headed from Miami to Houston, officials have said.

NTSB has recovered the flight data recorder from the cargo jet that crashed in Trinity Bay in Anahuac, TX. FDR being transported to NTSB labs in DC for evaluation.

#Anahuac pic.twitter.com/qzGHYyf6sD — NTSB_Newsroom (@NTSB_Newsroom) March 3, 2019

The cockpit voice recorder indicates that the crew was in communication with air traffic control and were being provided radar vectors for a runway approach at Houston’s George Bush Intercontinental Airport before the crash, the NTSB said Tuesday. The safety board cautioned the information was preliminary and subject to change.

NTSB Chairman Robert Sumwalt said on the night of the crash that preliminary information indicates "the aircraft was in what I would characterize as a normal descent, and at around 6,300 feet it began what I would characterize as a very, very rapid descent at that point."

Local and federal officials gather at a staging area during the investigation of a plane crash in Trinity Bay in Anahuac, Texas on Feb. 23, 2019. Brett Coomer / Houston Chronicle via AP

There was a simultaneous loss of air traffic control radar contact and communications with the aircraft and pilots, Sumwalt said at that time.

The cause of the crash is still under investigation. The quality of the audio recovered from the voice recorder was characterized as poor.

"There are times during the recording when the content of crew discussion is difficult to determine, at other times the content can be determined using advanced audio filtering," the NTSB said.