DUBAI, United Arab Emirates (AP) — A small plane involved in upgrading a runway at Dubai International Airport crashed Thursday night, killing four people and halting traffic at the world's busiest airport for international travel for nearly an hour.

Authorities gave no explanation for what caused the crash of the aircraft, a Diamond DA62 with a tail number belonging to Flight Calibrations Service Ltd. of Shoreham, England.

The UAE's General Civil Aviation Authority said all four people on board, three British citizens and one South African, were killed in the crash that took place 3 miles (5 kilometers) south of the airport.

Dubai International Airport, home to long-haul carrier Emirates, is the world's busiest airport for international travel. The airport said it halted flights from 7:36 p.m. until 8:22 p.m. over the crash.

Flight Calibrations Service announced in November it signed a contract at Dubai International Airport to do work on its "navaids," beacons surrounding an airport that help pilots know where runways are and how to land. Dubai International Airport later told The Associated Press that the plane "was being used to calibrate the approach systems" at the airport.

An employee at Flight Calibrations Services, which has two Diamond DA62s stationed in the United Arab Emirates, declined to comment on the crash Thursday night.

The work comes as Dubai has shut down its southern runway to resurface it and replace all its lighting and supporting infrastructure. It closed on April 16 and officials hope to reopen it on May 30.

Dubai has cut back on some of its scheduled flights and redirected others to Al Maktoum Airport at Dubai World Central, the city's second airport.

Dubai is a major city in the United Arab Emirates, a federation of seven sheikhdoms on the Arabian Peninsula.

The city-state's last major aircraft incident happened on Aug. 3, 2016. An Emirates Boeing 777-300 coming from Thiruvananthapuram, India, crash landed, but no lives were lost among its 300 passengers and crew. A firefighter was killed in a subsequent explosion of Flight EK521.

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