India, Sept. 24 -- The fire at a sleeper bus in Greater Noida that killed nine people was caused after a spark in the bus's air-conditioning system set the engine lubricating oil ablaze, police have said.

The incident took place around 11pm on Wednesday near Dayanatpur village in Jewar, on the Yamuna Expressway. The Bihar-registered bus was travelling from Noida to Mahoba with 35 passengers onboard.

According to Greater Noida police, "the fire broke out after a spark or blast in the bus's AC caused the engine lubricating oil to catch fire, allowing the flames to spread rapidly."

A few passengers noticed a burning smell after the bus reached the Yamuna Expressway and asked the driver to stop, Jewar station house officer Ajay Kumar Singh...