A search operation is under way for a cargo aircraft carrying five crew members that disappeared off the coast of Karachi, Pakistani aviation authorities said.

According to multiple local sources and the BBC, the Boeing 737 lost contact with air traffic controllers on July 7 at 21:21 local time after rapidly descending. The aircraft was travelling from Sharjah in the United Arab Emirates to Karachi.

Pakistan’s airport authority said the plane reported a navigation system issue shortly before beginning its descent.

The aircraft was operated by K2 Airways, a private cargo carrier based in Karachi that was established in 2018.

K2 Airways said it was co-operating with the Pakistan Civil Aviation Authority and other government agencies. The airline identified the five crew members on board and said efforts were continuing to locate them.

Preliminary data from Flightradar24 showed a sharp altitude fluctuation followed by a steep descent before the aircraft disappeared from tracking systems.

Pakistan’s navy and air force, along with other agencies, have been deployed as part of the search effort.