The train came off the track about 6 p.m. as it traveled toward the Central Station in this northwest English city, police said.

Emergency services were dispatched to the accident and assisted passengers off the train and out through the underground tunnel.

Merseyside Police said there were no injuries but a couple of people suffered panic attacks.

Assistant chief constable Helen King said the accident appeared to have been caused by a mechanical fault.

"All the indications suggest this was caused by some kind of mechanical failure, there is nothing to indicate any type of criminal attack, we want to reassure people of that," King said.

British Transport Police said the train derailed at a low speed.

Merseyrail, the company which operates Liverpool's underground train service, said they would launch a full investigation into the derailment.

There have been several fatal train accidents in Britain in recent years.

Last November, a passenger train slammed into a car at a railroad crossing west of London, killing six people and injuring 36 others. Seven people were killed and 11 seriously injured in May 2002 when an express train derailed at Potters Bar, north of London. In October 2000, four people died and 102 others were injured when a train derailed at Hatfield, north of London.