Nine people were killed, including one foreigner, and 57 others were injured, some of them very seriously.
Home Minister Palaniappan Chidambaram says tests confirm the explosion was caused by a bomb left in an unattended bag.
He told reporters on Sunday the nationality of the dead foreigner is not yet confirmed.
The bakery is close to the Osho Ashram frequented by foreigners for meditation practices.
Officials earlier said an unattended package was found in the bakery by one of the waiters. It exploded when he attempted to open it.
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