SALT LAKE CITY (AP) — Authorities say three firefighters have been injured after a fast-moving grass fire burned nearly 100 acres near Salt Lake City's Ensign Peak.

City fire officials say they had to evacuate 40 houses as a precaution Tuesday before the fire was knocked down.

They say two firefighters were hospitalized with heat exhaustion and smoke inhalation and another suffered a leg injury.

Authorities say two residents also were hospitalized with smoke inhalation.

Up to 60 firefighters responded to the fire. Its cause isn't immediately known.

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Information from: The Salt Lake Tribune, http://www.sltrib.com