A bomb scare on a Shanghai Metro train caused panic at lunchtime yesterday as it pulled into the Nanjing Road W. Station.

A Shanghai Daily reporter on the Line 2 train from Jing'an Temple witnessed 50 or more passengers running in panic from the rear of the 8-carriage train to the front after a man shouted there was a bomb onboard.

There were cries of: "Run!" "A bomb has been planted on the train!" and "It's about to explode!" as the passengers pushed their way forward, urging other passengers to get up from their seats.

They were being led by the man who sparked the incident. About 30 years old, 1.67 meters tall and wearing a T-shirt with pink and white stripes, he was shouting that he had spotted a male passenger with a suspicious bag in the rear compartment. The passenger had told him it was a bomb.

Raising the alarm just after the loudspeaker announcement that the train was about to arrive at the station, the man kept shouting "The bomber is coming!"

Police cordoned off the station after the incident but a thorough search of the train and the station found nothing.

They are now searching for the man who raised the alarm. Police said their investigation showed that the passenger with the "suspicious bag" didn't exist.

However, the incident highlighted the lack of emergency evacuation measures at the station, raising concern over potential accidents while passengers were running around in panic amid scenes of chaos.

On the train itself, many passengers fell to the floor and were trampled on. They included several elderly women. Some suffered light bruises but no one was seriously injured.

At the packed front of the train, with nowhere else to go, passengers began banging on the doors trying to get the driver to open them quickly. No one used the emergency brake system as the train was already slowing to a stop.

Some children were seen crouching against the windows on the seats, covering their ears with hands, shaking in fear. Almost all the passengers on the train reached the first two compartments, leaving the others empty.

When the doors opened there was a mad scramble to get out, with cell phones, handbags and transport cards falling to the floor and being left behind in the panic.

Despite warnings from passengers leaving the train, many people still got on, some of them picking up items that the fleeing passengers had dropped.

The train, again loaded with passengers and unchecked by security guards to see whether there was a bomb inside, continued its journey.

A crowd of passengers began arguing with the staff at the station, asking why security checks had failed to detect the bomb they believed was on the train, and why the train was allowed to continue on its way.

Many said that if the incident had happened during rush hour there could have been fatal consequences.

"Fortunately there were not too many people in the train, otherwise there could be deadly treading accidents," said a female passenger. "When such things happened, the only idea I got was to run, as everyone else was running."

The Metro operator halted the next incoming train and police with hand-held explosive detectors and sniffer dogs arrived. Entry to the station was blocked for just over 15 minutes.

That man who started the panic left the scene after getting off the train.

Police said they had identified him from surveillance tapes with the help of passengers, and were now in the process of tracking him down.