The NIA, which is probing the case, is yet to make any breakthrough.
"Five days after the serial bomb explosions, no concrete leads (have come up) so far and NIA has sent 18 samples collected as evidence for DNA touch test to Hyderabad," said a police official in Gaya, about 100 km from here.
The NIA officials also began to question private security guards of the Bodh Gaya Temple Management Committee who are responsible for the internal security of the temple complex.
Though NIA began a probe into the serial bomb explosions Sunday night itself, it formally took over the investigation after Bihar Chief Minister Nitish Kumar requested the union home ministry Tuesday.
The NIA detained six people and released all of them after questioning.
The Bodh Gaya temple is a Unesco World Heritage site. It is where the Buddha, who was born in neighbouring Nepal, attained enlightenment around 2,550 years ago.
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