With the annual monsoon rains soaking the city on Wednesday morning, police picked through the wreckage of carriages, placing evidence in bags and driving away onlookers.
A police inspector said: "We are just trying to establish what kind of explosives were used and where exactly the bombs were placed but it appears they were kept in the luggage racks."
His assessment matched initial reports that most of the victims suffered head and chest injuries, presumably from blasts above their heads.
Eight bombs tore through seven packed trains within minutes of each other during the evening rush hour in Mumbai, India's financial capital with 16 million residents.
Fear and worry
However, residents returned to the trains early in the morning. But there was none of the usual crush on the trains, which serve about six million people a day, making it one of the world's most crowded rail networks.
Many residents searched through the night for missing friends and relatives. Dozens of people stood in hospitals, carrying pictures of the missing.
Hospitals battled through the
night to treat hundreds of victims
Hospitals posted lists of the dead and wounded on notice boards and the Mumbai police has also listed the names on its website.
Many victims still remained unidentified.
Long lines of people waiting to donate blood formed at hospitals.
Suspicion for the blasts quickly fell on Kashmiri groups which have in the past carried out near-simultaneous attacks on Indian cities, including bombings last year at three markets in New Delhi that killed 59 people.
Indian intelligence officials believe that two groups, the Pakistan-based Lashkar-e-Tayyaba and the banned Students Islamic Movement of India, were behind the blasts, the Times of India newspaper reported.
Both groups were blamed for bombings in Mumbai in 2003.