Here are 10 latest developments
The twin explosions took place in two sleeper coaches 10 minutes after the Guwahati - Bangalore Express pulled into the train station.
One of the blasts took place below the seat of a 24-year-old woman who was killed immediately, said officials. She was traveling from Bangalore in Karnataka to Vijaywada in Andhra Pradesh.
Nobody has been arrested or detained so far, said the Tamil Nadu police.
The National Investigation Agency, which usually looks into terror attacks, has sent representatives to collect and examine evidence
The train had left Guwahati on Tuesday and was headed to Bangalore. It was running about two hours late. The train has now left Chennai station after receiving the requisite security clearance. (Images: Blasts at Chennai railway station)
The Tamil Nadu police says that because the train was delayed, it suspects that Chennai was not the target.
Railways Minister Mallikarjun Kharge said two passengers have been badly hurt and 12 others have minor injuries.
Tamil Nadu's most senior police officer K Ramanujam said, "It is not a major blast". He added, "It is premature to say what kind of device was used is the blast. Damage to the train is not heavy."
Bomb disposal squads and sniffer dogs are patrolling the station.
The Bangalore helpline is 080 22876288; the Chennai helpline is 044 25357398.
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