Airports, railway stations and tourist centres are being heavily protected by police after the attacks which struck at the heart of the financial capital.
World leaders condemned Monday's blasts while Indian politcians began speculating over who was behind the attacks.
The targets were designed to achieve maximum loss of life, say investigators. No one has claimed responsibility but politicians are poitning the finger of blame at Muslim activists.
A senior state minister in India has linked the twin car bombs to the anti-Muslim riots in the western state of Gujarat last year.
Inter-communal rioting in Gujarat state last year saw 2000 people killed, most of them Muslims.
The India media also speculated that Monday’s attacks could be aimed at the Gujarat community in Mumbai in retaliation for the Gujarat rioting.
The Hindustan Times said the bombs were placed in an area dominated by Gujarati jewellers and traders.
"It is true that the blasts have taken place in Gujarati populated places," said deputy chief minister of Maharashta state Chhagan Bhujpal.
Meanwhile, State Home Minister Kripa Shankar Singh said the bombings in India’s commercial hub may be the work of pro-Pakistan group Lashkar-e-Taiba.
“We believe it could be work of the groups such as Lashkar-e-Taiba or some other radical Islamic group,” he said on Tuesday.
New Delhi accuses the group of being behind an attack on its parliament in December 2001 which left 15 people killed, including the five attackers and almost brought India and Pakistan to war.
Heightened security across India
Two bombs hidden in taxis detonated seven minutes apart on Monday during the lunch-hour rush near the Hindu temple of Mumbadevi in the old city and a square in front of the colonial Gateway of India monument.
Mumbai’s police commissioner RS Sharma has said they have information on who could be behind the attacks but would not reveal any names since it would hamper investigations.
Singh said that while no group has claimed responsibility for the blast, the tactic was similar to earlier attacks in Mumbai, including the last one in July on a bus which left 12 people dead.
Police blamed those blasts on a banned group, the Students’ Islamic Movement of India (SIMI), which is accused of ties with Lashkar.
But India’s Deputy Prime Minister Lal Krishna Advani said investigators had no concrete evidence linking SIMI to the attacks.
India banned SIMI after accusing the group of fuelling sectarian violence in the country.
Tensions rose on Monday after police said they had found nine detonators on rail tracks near the city of Nasik, some 200km north of Mumbai where thousands of Hindu pilgrims have gathered for a religious festival.
The twin blasts came minutes after archaeologists claimed a grand Hindu temple had been found below the surface of a mosque razed by Hindu zealots in 1992 in northern India.
That sacrilege sparked Hindu-Muslim riots which left thousands dead.