A Cathay Pacific Airways training flight made an emergency landing at Hong Kong International Airport after a problem with one of its engines was discovered on Monday.

Training flight CX9993 with no passengers or cargo but an unknown number of crew members took off from the city's airport to Zhuhai Jinwan Airport in neighbouring Guangdong province.

But one of the engines of the twin-engine Airbus A330-300 was found to have problems when flying over Zhuhai at about 1pm, prompting it to head back to Hong Kong, according to the Civil Aviation Department.

Zhuhai's air traffic control authorities were alerted.

The department's air traffic control staff declared a "full emergency" after it noted the situation at about 1:00 p.m. An arrangement for an emergency landing was initiated.

A full emergency is declared when an aircraft is known or suspected to be in such trouble that the danger of an accident exists. The Fire Services Department then fully mobilises its fire and rescue services.

The department deployed 26 fire engines, nine ambulances, seven fire vessels, and 160 firefighters and ambulance crew members.

The flight landed at Hong Kong airport at 1:14 p.m. Cathay Pacific said all aboard the aircraft left the plane "as usual".

No injuries were reported.

An Airport Authority spokesman said air traffic and airport operations were not affected.

According to online flight tracking service Flightradar24, the aircraft departed Hong Kong at about 12:00 p.m. Monday. It made a circle above Zhuhai before heading back. It descended from 7,000 to 1,200 feet above ground in about 10 minutes in Zhuhai, before climbing to 6,000 feet.

The Civil Aviation Department said the airline had submitted a report, and the department said it would follow it up.