Seven plastic pipes filled with what appeared to be firecracker powder, connected to batteries with wires, were found on the train when it was being cleaned up at Kurla carshed, a Mumbai police official said.
A letter with a mobile number and an unidentified man's photograph were also found along with the pipes, said senior police inspector Sushil Kamble of Tilaknagar police station, who is investigating the case.
"We are examining the letter and trying to contact the mobile number," he said.
While railway officials initially said the suspicious materials found on the train appeared to be gelatin sticks, Kamble said they were plastic pipes.
The seized materials were sent to a forensic science laboratory for further investigation, he said.
The train had arrived at Lokmanya Tilak Terminus (LTT) in the city at 7.30 in the morning.
S K Jain, divisional railway manager of the Central Railway, said the explosives did not seem to be highly dangerous, but the discovery was taken seriously and the matter was being investigated thoroughly.
