Investigators on Friday searched a number of locations and picked up about a dozen suspected operatives of the home-grown Islamist terror organisation Indian Mujahideen as authorities were still looking for leads in the probe into the deadly triple blasts that hit Mumbai on Wednesday.

As officials claimed that no definite clue was found two days after the bombings, informed sources claimed that multiple raids were conducted following a suspicion that it may have been an operation of the Indian Mujahideen modules from Hyderabad, Karnataka and Jharkhand with the help of some local support.

They said 12 suspects of the terror outfit, which had previously owned up responsibility for similar terror strikes in Indian cities, were picked up from various locations across the country in the search operations.

The sources said the outfit may have formed a new module with recruits from varous cities after keeping a low profile in the past year.

Police sources in Jharkhand capital Ranchi said that a team of the National Investigation Agency (NIA) searched the home of Manzar Imam in connection with the Mumbai bombings that killed 17 people.

However, Imam, said to be in his 30s, had gone out for some treatment when the team from India's premier anti-terror probe agency searched his home. The sources said the NIA sleuths spoke to his family and searched his computer for information.

Imam, the sources said, is a neighbour and friend of Danish, whose name figured in the probe into the 2008 Ahmedabad serial bombings, in which at least 50 people were killed.

"My son is being implicated as he was a friend of Danish," said Manzar's father Ali Imam.

According to the sources, Danish's mail was tracked by investigating agencies who believed that some Ranchi youth were associated with the Indian Mujahideen.

The NIA sleuths have also been sent to Karnataka and Hyderabad where they are probing the recent activities of the suspects of the Indian Mujahideen and Students Islamic Movement of India (SIMI).

Sources said that examination of the CCTV footage, collected from Wenesday evening's blast sites, has so far hinted that the terrorists who planted the bombs may not have been locals from Mumbai.

The sources said that the Intelligence Bureau had received an input from Hyderabad in February that some Indian Mujahideen men were planning to strike.

But the information could not be followed up because the terrorists have stopped using cellphones and emails, they said, and added that they may have met in person.

The investigators are also working on a theory that the terrorists, who could be more than one, who planted the bombs may have used a 'safe house' in areas near the blast sites in Mumbai to manufacture the bombs.

The theory is based on the fact that the bombs were Improvised Explosive Devices made with ammonium nitrate and fuel oil, called ANFO. The sources added that it is difficult and dangerous to travel long distances with the prepared IED as it is unstable and can detonate by even a slight spark.

Even police patrolling at various places in and around Mumbai is so intense that the bombers may not have taken the risk of being caught with a bomb, they said.

Two of the three blast sites - Zaveri Bazaar and Opera House are separated by a little over a kilometre and Dadar, the third site, is about 12 km away.

That means, if a 'safe house' was used it could be close to or around Zaveri Bazaar or Opera House.