SIMI VALLEY (CBSLA.com) — Fire crews on Wednesday evening battled a fast-moving brush fire in Simi Valley.

The fire was first reported at around 5:30 p.m. in an isolated hillside area near the Wood Ranch neighborhood of Simi Valley.

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The fire began spreading quickly and was reported to have scorched 40 acres at 7 p.m. The fire was 50 percent contained at 7:30 p.m.

Warm and dry weather created difficult firefighting conditions.

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One-hundred firefighters were on the seen at 7 p.m. and three firefighting helicopters were making water drops.

By 9 p.m., firefighters said they had stopped forward progress on the fire.

No homes or structures were threatened, firefighters said.

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Firefighters were planning to remain at the scene throughout the night.