Police found 19 unexploded bombs in a southern Indian city a day after at least 40 people were killed in blasts a state chief minister blamed on Islamic militants based in Bangladesh or Pakistan.
New Delhi has sent extra police and special bomb detection equipment to Hyderabad, an IT hub with a history of Muslim-Hindu tensions, after bombs packed with metal pellets exploded at a food centre and an amusement park on Saturday night.
About 80 people were wounded by the three blasts that went off within minutes of each other.
Police discovered the unexploded bombs - most fitted with timers and placed in plastic bags - at bus stops, by cinema halls, road junctions and pedestrian bridges and near a public water tap across the capital of Andhra Pradesh state.
The chief minister of Andhra Pradesh pointed to Islamist militant groups in neighbouring Pakistan and Bangladesh.
"As things stand today the available information points to that," Y.S. Rajasekhara Reddy told a news conference when asked if militants from Bangladesh or Pakistan were involved.
A federal home ministry official said about 22 people were being questioned. Separately, police reported one man had been detained near Hyderabad on suspicion of selling bicycle ball-bearings that were used as pellets in the bombs.
Reddy said 40 people had died, including three children, while the state home minister and some police put the toll at 43.