(Bloomberg) -- The National Transportation Safety Board and the Federal Aviation Administration have begun investigating an incident involving a Southwest Airlines Co. jet that allegedly took off from a closed runway earlier this week. 

Flight 4805 took off from Portland, Maine, at about 5:45 am local time on Tuesday en route to Baltimore, according to data from tracking website FlightRadar24. The FAA said that the Boeing Co. 737 jet departed from a temporarily closed runway and that an airport vehicle exited the runway before it began its takeoff roll. 

The NTSB plans to release a preliminary report on the incident in 30 days that will contain information gathered in the initial phase of its probe, according to a statement. The final report into the incident will take 12-24 months, the NTSB said. 

Southwest is engaged with the NTSB and the FAA to understand the circumstances around the incident, a spokesperson for the carrier said in a statement Friday. “After departure, the aircraft continued safely to its destination,” the spokesperson said, referring any additional questions to the NTSB. 

The event comes amid a spate of incidents involving the airline, including an unusual rolling movement known as a “Dutch roll” that occurred on a 737 Max operated by Southwest in May. Bloomberg also previously reported that a Southwest flight in April plunged to within 400 feet of the ocean off the coast of Hawaii before flight crew pulled up and safely returned to its departure airport. 

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