Officials are still trying to figure out the cause behind a Monday night blaze on the Bay Bridge that closed multiple lanes for over an hour.

It was 10 p.m. Monday when the California Highway Patrol received reports of flames shooting up into eastbound traffic from a grate just east of the Treasure Island exit.

According to a CHP spokesperson, lanes #1 and #2 of the new, Eastern span of the Bay Bridge were closed until about 11:17 as crews extinguished the fire.

A CHP spokesperson says that no one was injured in the blaze, and they have not received any reports of damage to vehicles.

But why did it start in the first place? That's still a bit of a mystery.

"CHP said it looked like some debris accumulated in the expansion joint, and that it may have been started by a cigarette," KRON4 reports, but that theory has yet to be confirmed. That confirmation (or lack thereof) will come from Caltrans engineers, who are expected to mount a follow-up investigation to determine if this was a freak, one-time thing, or if we can expect the new span of the Bay Bridge to routinely burst into flames.