The incident happened around 1.30 PM when one bus of route no E1 started its journey from Jadavpur 8B bus stand.
On reaching the Jadavpur Police Station crossing the driver noticed black smoke coming out of the engine following which passengers rushed out of the bus, a senior officer of Kolkata Police said.
This lead to a huge traffic jam in the area, police said.
According to eye-witnesses, locals helped in dousing the fire and rest of the work was completed by two fire tenders which reached the place later.
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