Four foreign nationals were killed when a small plane crashed at London Southend Airport on Sunday shortly after takeoff, British police said on Monday.

The U.S.-built Beechcraft B200 Super King Air plane had been bound for the Netherlands, when it “got into difficulty and crashed within the airport boundary,” Essex Police Detective Chief Superintendent Morgan Cronin told reporters.

A plume of black smoke rises from an area near the runway after a small plane crash, as seen from inside a building at London Southend Airport

Southend Airport, which is located about 35 miles east of the capital and used by easyJet EZJ.L to fly to European holiday destinations, will remain closed until further notice, the airport’s CEO Jude Winstanley said.

Britain’s Air Accidents Investigation Branch, which investigates civil aircraft accidents, said it was “too early” to determine what caused the crash. It has deployed eight inspectors to the site.