HONG KONG, Feb. 14  -- Fire broke out on a train when it was running in a tunnel in the west of Hong Kong on Wednesday morning, and about 650 passengers were evacuated.

The incident occurred inside the Tai Lam tunnel in the New Territories shortly after 9 a.m. as the train was heading from Tin Shui Wai to Mei Foo station in the west of the New Territories. Smoke reportedly poured out of one of the carriages of the train.

About 650 passengers were evacuated from the train. Because it was dark in the tunnel, it took almost 30 minutes for people to walk out.

Four men and five women, aged 17 to 40, felt sick and were sent to a hospital nearby. They are in stable condition, local police said. Another man, aged 43, was sent to another hospital for observation.

The Environment, Transport and Works Bureau is concerned about the incident and has ordered the Kowloon-Canton Railway Corporation (KCRC) to submit a report as soon as possible.

The bureau has also asked the corporation to check the power-supply equipment of all trains of the same model.

The Rail Inspectorate is investigating the cause of the incident and will ensure that the incident was not caused by failure of equipment inside the tunnel before approving the resumption of West Rail service at Tai Lam Tunnel section.

Initial investigations show that the oil leakage from a transformer on the rooftop of the affected carriage was the cause of the fire, the corporation said.

Apologizing for the incident, the corporation said it will conduct a thorough investigation and check other transformers of the same model in other trains.