CLAYTON (CBS SF) — The Marsh Complex fire, first reported early Saturday morning northeast of Mount Diablo in unincorporated Contra Costa County, was at 85 percent containment Sunday night, and holding steady at 655 acres, Cal Fire said.

Approximately 75 firefighters from Cal Fire and from the East Bay Regional Park District, San Ramon Valley and East Contra Costa fire departments are mostly mopping up Sunday night, working to get the last remnants of the blaze out, said Cal Fire Division Chief Jonathan Cox.

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The burned acreage has not increased from Saturday night.

“We want to make sure 100 percent of the hot spots are mopped up before was call 100 percent containment,” Cox said. “We’re optimistic we’ve turned the corner on this one.”

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As many as 400 firefighters had been on the fire lines Saturday, when more than a dozen separate small fires along Marsh Creek road east of Clayton merged into three larger blazes. No structures have been lost; one firefighter suffered heat-related health issues Saturday.

It is expected that firefighters will be on the scene into Monday making sure the fire is all the way out. The fire’s cause, Cox said, remains under investigation.

The Contra Costa County Sheriff’s Office said that Marsh Creek Road remains closed due to the blaze, except for residents.

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