Technicians work next to the damaged engine of a Qantas Airways A380 passenger plane after it was forced to make an emergency landing at Changi airport in Singapore. (Vivek Prakash/Reuters)

Qantas Airways Ltd. has grounded its fleet of Airbus A380 jumbo jets after one of the planes made an emergency landing in Singapore due to mid-air engine trouble, the company said Thursday.

One of the A380's four engines experienced "engine issues" about 15 minutes after it took off from Singapore, company spokeswoman Emma Kearns said. She said the plane can fly on three engines, but the pilot returned to Singapore to be safe.

The Sydney-bound plane carrying 440 passengers and 26 crew landed safely, the company said.

After the plane touched down in Singapore, the engine closest to the fuselage on the left wing had visible burn marks and was missing a section of plate that would have been painted with the red kangaroo logo of the airline. The upper part of the left wing also appeared to have suffered some damage.

Qantas is investigating the incident and Qantas CEO Alan Joyce said in a statement that the company was suspending operations of its six A380s until "we are confident that Qantas safety requirements have been met."

"The A380 for us is a fantastic aircraft," Joyce said. "This issue — an engine failure — has been one that we haven't seen before."

He said the airline was taking the incident seriously because it was a "significant engine failure."

The cause of the engine failure was not immediately clear and the company said there was no explosion — but witnesses aboard the plane and on the ground reported blasts.

'Yellow flames came out'

"There was this huge, kind of loud bang," said Lars Sandberg, one of the passengers on the plane. "People were visibly shaken, I was shaken."

He said passengers looked out the left side of the plane to try and see what the problem was, and that the pilot eventually told passengers it was a failure of the second jet engine.

One passenger, Rosemary Hegardy, 60, of Sydney, told The Associated Press that she heard two bangs and saw yellow flames from her window.

"There was flames, yellow flames came out, and debris came off.... You could see black things shooting through the smoke, like bits of debris," she said.

The engine trouble happened over the Indonesian island of Batam, reports said. The Sydney Morning Herald quoted an Australian resident of Batam Island as saying an explosion was heard in the air and that debris fell on a residential area.

Indonesia's most volatile volcano, Mount Merapi, has been belching clouds of ash into the sky about 1,400 kilometres west of Batam, forcing the closure of some air routes near the mountain.

The airline had no immediate comment on whether the engine trouble was related to eruptions of Mount Merapi over the past 10 days. However, officials from Indonesia said the volcanic ash did not cause the jet's engine problem.

"The shutdown of the Qantas engine had no connection with Mount Merapi," said Bambang Ervan, a spokesman for Indonesia's Transportation Ministry. "It was too far from the volcano — the sky over Singapore and Sumatra island is free of dust."

Thursday's emergency landing was most serious mid-air incident involving the A380, which is the world's largest jetliner. The A380 made its debut in October 2007 with Singapore Airlines flights to Sydney, the same route that Qantas flight QF34 was flying when it was stricken.

Singapore Airlines, which operates 11 Airbus A380s originally said it would not ground its planes, but later said in a statement that it would be "delaying all flights operating our A380 aircraft" after engine-maker Rolls-Royce and Airbus advised it to conduct precautionary technical checks.

Airbus said in a statement that it was providing all necessary technical assistance to the investigation and a team of specialists from Airbus was being sent to Singapore.

Rolls-Royce also said it was aware of the situation, noting that the investigation was still at an early stage.

With files from The Associated Press