Central Railway officials say the explosion, which took place in the coach next to the motorman's cabin, occurred at around 7.34 pm when the A-51-Dn Ambernath fast was approaching a level-crossing before pulling into Vikhroli station. Commuters and members of the public were still milling around the platform an hour later as police personnel crowded the platform. Railway police believe the explosive, whose nature is being studied, was in a briefcase resting near a commuter, Lakwinder Surjeet Singh (35).

Singh, who sustained a compounded fracture, has been admitted to Rajawadi Hospital at Ghatkopar. Policebelieve he could be the key suspect. Singh, who boarded the train at Ghatkopar, told Experess Newsline

: ``I couldn't figure out what had happended when the blast took place. I felt a burning sensation on my leg. There was confusion till somebody pulled the chain and the train came to a halt.'' Eyewitness claim there were two other Sikh commuters with Lakwinder. Both, however, are untraceable.

A Kalyan-bound passenger, Dilip Bhagat, was administered first-aid at the station and released, police say. After the train was evacuated, it was taken to a spot near Bhandup station at around 8.32 pm.

A team of experts and sniffer dogs are studying the nature of the explosive though preliminary investigations rule out the deadly RDX. They suspect it was a highly imflamable material that was activated by the rough and tumble of the rush-hour traffic. Police, though, are not ruling out the possibility of sabotage in the aftermath of the Kargil conflict just yet.

Assistant Deputy Railway Manager P KSrivastava, Commercial Manager Naresh Goel and Superintendant of Police (Railways) T S Bal were taking stock of the situation at Vikhroli station till late this evening.