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 Diamond DA62 aircraft with a tail number belonging to Flight Calibrations Service Ltd. of Shoreham, England.

The UAE's General Civil Aviation Authority said the three British citizens and one South African on the plane were killed.

Early Friday morning, police, paramedics and flight investigators worked at the crash site, some 8 kilometers (5 miles) southeast of the airport in Mushrif Park near the city-state's water reservoirs.

Police told Associated Press journalists they could not visit the crash site, which was hidden from view by sand dunes.

The airport, home to long-haul carrier Emirates, is the world's busiest for international travel. 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 to work on the airport's “navaids,” the beacons around an airport that show pilots where runways are and how to land on them. 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 for resurfacing and replacing the light and support 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.