HONG KONG • A passenger train derailed during the morning rush hour in Hong Kong yesterday, leaving eight people injured.

Images from the scene showed three carriages off the tracks and zigzagged across the rails near Hung Hom station in Kowloon - a busy interchange that provides services to mainland China.

Passengers had to leave the train through a broken door and cross tracks of the East Rail Line to get to safety.

Five hundred passengers were evacuated from the train. Eight passengers reported injuries when they arrived at the concourse of the station, said the authorities.

Of those injured, five had to be taken to the hospital for treatment and were "in conscious condition", said a senior officer from the Fire Service Department. Their injuries were mostly on the neck and shoulders, according to firefighters.

A passenger who gave his surname as Kwok said he heard noises shortly before the accident, and the train was swaying before it derailed.

Mr Kwok, who was seated at the time, bumped his head against the handle of the seat in front of him. Another man who identified himself as Chung said he felt a strong force of braking.

The cause of the derailment is under investigation but there is no suspicion of foul play at this point despite earlier attacks by pro-democracy protesters on the city's mass transit system.

"We will not rule out any possibility but at this stage, we won't speculate," Transport and Housing Secretary Frank Chan told reporters.

Mr Adi Lau, operations director of the rail company, MTR Corporation, told the media that a short section of the track near where the incident happened yesterday was replaced on Monday. He added that based on his visual assessment, there was nothing "unusual" about the replacement.

When asked by the media at the scene whether the incident was the result of a sabotage or a mechanical problem, Mr Alfred Sit, director of electrical and mechanical services, said: "We will carry out an independent, thorough and in-depth investigation."

He added that it will take three to six months for the department to complete the investigation and submit a report.

Preliminary investigation showed a small crack on the track, said the Fire Service Department. But it was not known if the crack was there before the derailment or was a result of the derailment.

Subway services between two stations on the line were suspended and intercity services to mainland Chinese cities, including Guangzhou, Dongguan and Beijing, were cancelled for the day, said MTR.

Hong Kong is in its fourth month of political unrest, which has seen millions of protesters hit the streets in the biggest challenge to Chinese rule since the city's handover from Britain in 1997.

Sparked by a now-withdrawn Bill to allow extraditions to the mainland, the protests have turned increasingly violent, with clashes between police and hard-core protesters becoming frequent.

MTR has been targeted by protesters since the company initially refused to hand over CCTV footage of police last month beating demonstrators and passengers on a subway train. Protesters have vented their fury by vandalising entrance barriers and ticketing machines as well as smashing windows in several stations.

MTR chief executive Jacob Kam told the Financial Times in an interview published before the derailment that the protests were an unprecedented challenge and that the firm has been struggling to cope.

"It is getting more and more difficult because we are running out of spares," he said.

"In fact, what we've done is we have cannibalised parts from other stations and brought them to the damaged stations to try to keep things running."

AGENCE FRANCE-PRESSE, XINHUA