The fast train coming from Bhayander rammed into the dead end on platform no.3 of Churchgate station at around 11.25 AM when the motorman could not stop the local.
As a result, the first coach of the train jumped onto the south-end concourse of the platform and was seen lying in a tilted position.
The reason for the motorman not being able to halt the train was yet to be ascertained.
"It would be premature to speak about the cause of the accident. The exact reason can be ascertained only after proper investigation," Western Railway's (WR) chief PRO Sharat Chandrayan said.
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"We are enquiring with the motorman, L S Tiwary, who received mild injuries, and as per the normal procedure, we would also be checking whether he was under the influence of alcohol," said another senior official involved in the process of investigation.
The impact of the train's collision with the platform's dead end was so huge that the wheels of the first coach got hanged into the air, ripping apart all the technical equipment in its lower part and also the overhead wire.
The injured woman was admitted to hospital, he said.
The mishap affected the train services which were running late by almost an hour.
"I boarded the train at Vile Parle station at 12.15 PM which reached Churchgate at 2 PM when it should have ideally reached by around 1 PM," said Manisha Rege, a media professional.
Commuters were seen clicking pictures at the site from their mobile phones.
"It looked like a scene from a Bollywood film. I wonder what would have happened to those who were in the first coach," said commuter Kirti Khot at the railway station.