Anthony Quadros, General Secretary, Bombay Taximen's Association, said the two taxis in which the explosives were placed have been identified.
Taxi number MH02-R-2022 was used in the Gateway blast, while taxi bearing the number plate MH02-R-4421 was used in the Zaveri Bazar explosion.
The taxis were registered at the Andheri Regional Transport Office and were stationed between the suburbs of Khar and Andheri.
He confirmed the death of one driver in the Zaveri Bazar explosion. He said he is still making inquiries about the other driver.
In a telephonic conversation, he told rediff.com this was the first instance where the city's taxis had been used to cause such explosions.
"In the 1993 blasts they put bombs in private vehicles, then they targetted BEST buses. Now they are targetting taxis," said Quadros who rushed to Pydhonie -- the area where the first blast occurred -- as soon as he heard the news that a bomb had exploded in a taxi, but was compelled to return because of the traffic snarl.
Fearing Monday's blasts could hinder people from travelling by Mumbai's taxis, he said it was important that taxi drivers check their vehicles after the passenger had disembarked.
"We cannot check their (passengers') luggage, but I think drivers will have to check the insides after dropping passengers. The police need to help out on this, because taxis will require to halt for sometime even in no parking areas to do these checks."
Fifty thousand taxis ply in Mumbai. They transport 1.1 million commuters in the city every day.