Police are still searching the site of the blast for clues
Indian police are examining CCTV footage as they continue their investigation into Saturday's deadly blast in the western city of Pune.
At least nine people were killed and 57 others injured in the attack at a restaurant popular with tourists.
The bombing is the first major strike of its kind in India since the deadly Mumbai attacks in November 2008.
Meanwhile, Indian officials dismissed calls for upcoming talks with Pakistan to be suspended.
On Sunday Hindu nationalist leaders urged the government to call off talks scheduled for 25 February.
The blast came a day after India and Pakistan agreed to meet for the talks in Delhi - their first formal negotiations since the Mumbai attacks.
India blamed Lashkar-e-Taiba, a Pakistan-based militant organisation, for the attacks in which more than 170 people, including nine gunmen, died.
No conclusions could be drawn yet as to who was responsible for Saturday's blast, Indian Home Secretary GK Pillai was quoted by the Associated Press news agency as saying on Saturday.
Nobody has claimed responsibility for the Pune attack.
The explosion tore through the German Bakery restaurant, on North Main Road, at about 1900 local time (1330 GMT), when it was packed with diners.
Reports say an unattended package exploded when a waiter in the restaurant attempted to open it.
The German Bakery is near the Osho Ashram, a mystic centre popular with visitors to Pune.
The Chabad centre, run by the Jewish Orthodox Chabad-Lubavitch movement, whose members were targeted in the 2008 Mumbai attacks, is also in the area.
The Indian home ministry has advised all state governments to be on high alert.