Indian officials say the death toll from this week's bomb blasts in Mumbai has risen to 19 people, as police continue to investigate evidence to determine who was responsible.

Officials said Saturday two more people had died of the more than 130 injured in Wednesday's triple bomb blasts that shocked India's financial capital.

Teams of investigators have been sifting through forensic evidence and surveillance video for days, but still have not named any suspects.

Authorities also are questioning suspected members of militant organizations, despite the fact that no group has claimed responsibility.

While they refuse to speculate on who might be responsible, officials say they believe it was a coordinated terrorist attack and have not ruled out that Mumbai's criminal gangs were involved.

Forensic examination of debris at the sites already has indicated that ammonium nitrate – a common fertilizer ingredient – was used in the explosives. Officials say the improvised explosive devices used indicate some level of sophistication.

Wednesday's attack was the worst to hit India's financial hub since Pakistan-based militants laid siege to the city in 2008, killing 166 people.

Peace talks between the two countries were suspended following that attack and have just recently resumed. The Pakistani government condemned the violence immediately after the blasts.