From the BBC:

Hundreds of Muslims have been questioned by police in the Indian city of Mumbai following last week's serial bombings.

Suspicion has fallen on the Lashkar-e-Toiba, a Kashmiri militant group based in Pakistan, as well as radical Islamic groups based in India prompting the security agencies to concentrate their inquiries on the city's Muslim community for any leads.

This has created a growing sense of uneasiness among the city's four million Muslims, who have come out in strength to condemn the attacks.

Mumbai has a history of tensions between the city's Muslim minority and Hindu majority, although initial fears of a backlash targeting the community have proved unfounded.

From the Telegraph (UK):

As blame for the bombings falls on extremist Islamic groups within India, bringing the spotlight of suspicion to bear on the city's Muslim population, families of Muslims killed in the blasts are silently coming to terms with their grief....

In mosques, Friday prayers were dedicated to the victims and the condemnation of the blasts has been unequivocal. No display of anti-Muslim rancour has so far surfaced, but in a majority-Hindu country, Muslims remain scared of a backlash or police harassment.

From PBS:

Forensic experts have confirmed the bombs were left on luggage racks and all had timers, though they've yet to identify the explosive.

Many people have already made up their minds where blame lies. This protest in Delhi today. The home ministry has suggested it was the work of Lashkar-e-Taiba, the Pakistan-based terror outfit fighting Indian rule in Kashmir, working with a local, banned Islamic group.

Amid the grief here, there is impatience for results, but there is a danger of a serious backlash if the police are heavy-handed in Mumbai's Muslim communities.