EXPLOSITION PARK (CBSLA.com) — A day after a fiery crash in Exposition Park left seven people injured, police were still working to determine the cause.

Police said a speeding Mercedes Benz burst into flames Monday night after it crashed into the side of the bus in the 1600 block of West Martin Luther King Jr. Boulevard.

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Seconds later, police say, a speeding Dodge Challenger clipped the back-end of the bus, but the impact didn’t result in flames.

What followed was a pinball-like machine scenario.

The Challenger spun out of control and hit a car that was behind a bus traveling westbound on MLK; that vehicle spun out of control and hit a parked car.

Inside the parked car were two child, ages 8 and 11, who were uninjured. Their father, who was exiting the car, suffered a broken leg.

A day later, it remains unclear whether the Benz and Challenger were racing, though police have confirmed that they believe speed was a factor in the crash.

“Officer, I need to talk to you,” said one woman, who is seen in a YouTube clip moments after the crash. “These guys were racing. They almost crashed into me all the way back there.”

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Various cellphone video captured the dramatic moments.

It was also unclear whether the intense fire was the direct result of the fact that the bus operates on compressed natural gas.

The fire department said it could not provide a definitive answer. Neither could the LAPD.

But the fleet of buses from Metro has operated on compressed natural gas since 2011.

“I saw a big, old fire like come from the bus and you just see people running everywhere,” said a woman identified only as Malaysia, who took cellphone video moments after the crash.

Two LAPD officers and one man who was walking nearby rushed to the flames and helped remove at least four people from the burning cars.

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With the exception of a female driver, there were no passengers on the bus.