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A Montebello bus laying on the collector lane next to the 110 Freeway Friday morning.

DOWNTOWN LOS ANGELES — Montebello Bus Lines (MBL) are bringing in experts to determine what caused an empty bus to flip over onto the 110 freeway below.

The MBL released a statement late Friday afternoon confirming that "an empty Montebello bus waiting to be exchanged for another bus, flipped over onto the southbound 110 Fwy.," around 8 a.m. this morning.

"The out-of-service bus was a hybrid-electric bus purchased in 2009. It was parked west bound on 5th Street when it rolled back and landed on its right side onto the shoulder area of the Harbor Freeway below," the statement read.

“We have not been able to conclusively determine the cause of the accident. It is currently an open investigation. We are bringing in experts to assist us in conducting a thorough investigation. We’re grateful to report that no one was injured,” said Aurora Jackson Montebello Bus Lines Director of Transportation.

Cynthia Gibson, a spokesperson for the MBL told Blogdowntown that there is a black box on the bus and they are bringing in experts to further analyze the information as the initial investigation was inconclusive.

"The ramifications are serious," Gibson said, "so we dont want to speculate at this point."

Louie Fuentes who works Downtown was carpooling in to work when he saw the bus fall.

"Right before 4th Street came up we saw this big bus go down," Fuentes said. "It first came down on its rear and then it went on its side and then turned over."

Fuentes was the passenger in the car. He said he got out of the vehicle and ran to the downed bus because he was concerned.

"A couple of people ran with me," Fuentes said. "No passengers were in there. Then I was concerned for the driver. We looked under and around and didn't see him. We thought maybe he jumped out."

As it turned out the driver was not injured. He was nearby but not on the bus when it fell.

"There was no smoke," Fuentes said. "But I did see a lot of fuel. The bus was not running."

Fuentes said it was a fluke he was even on that side of Downtown since he usually comes in from the east.

"I usually dont drive that way," he said. "I just happened to drop off my car in Santa Monica. This was a once in a lifetime incident."