ANAHEIM (CBSLA.com) — A 300-foot gravel spill made a mess of the westbound 91 Freeway in Anaheim Thursday evening.

All but one lane of the freeway was closed after the spill, authorities said.

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The spill occurred around 7:25 p.m. near where the westbound 91 and northbound 57 Freeway meet.

The cause of the spill is under investigation.

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It was unclear how long it would take to clear traffic in the area.

Officials said they were hoping to have all the lanes cleared by 8:45 p.m. but reporting in Sky 9, Stu Mundel said, “that sounds to be very optimistic.”

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