Indian authorities are closely examining an email that may be a claim of responsibility for this week's deadly explosion in New Delhi.
Police have released two sketches of possible suspects and are looking for a car that may have been connected to a bomb attack Wednesday.
The explosion outside a high court killed at least 12 people and injured dozens more.
India's National Investigative Agency has offered more than $10,000 in reward money for information from the public leading to the terrorists who planted the bomb, believed to have been in a suitcase.
Police in Indian-controlled Kashmir detained three people who run a cyber cafe in the region. An email traced to a cybercafe allegedly claims responsibility for the attack on behalf of an Pakistan-based Islamic militant group.
Pakistan's government has condemned the bombing.
Jammu and Kashmir Chief Minister Omar Abdullah says the email is being investigated seriously.
"It is the responsibility of those who are tasked with protecting this country that they must provide answers as to who was responsible for this and to ensure that attacks like this do not succeed in the future," said Abdullah.
Wednesday's bombing is the deadliest attack in India since July's serial bombing of busy areas in Mumbai, when three bombs went off in rapid succession, killing 20.
Returning home from Bangladesh, Prime Minister Manmohan Singh was quoted as telling reporters on his plane that terrorists are able to take advantage of "unresolved problems and weaknesses" in Indian security.
A spokesman for India's main opposition party, Ravi Shankar Prasad, says more vigilance is needed.
Shankar said, "There is no proper security, and no intelligence beef up ... Terrorists come with impunity, and kill people with impunity ... How many innocent Indians will have to be killed more for the government to take those actions which can assure the public and deter the terrorists?"
Security experts recommend increased use of closed circuit cameras, and the establishment of a long-delayed national intelligence grid to better track the movements of suspected terrorists.