WALNUT CREEK (KPIX) — Fire crews in Contra Costa County were busy Thursday, responding to two separate fires that threatened homes.

Thursday afternoon shortly before 4 p.m., fire crews were called to a fire that broke out at an abandoned two-story house on Weaver Lane.

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The roof and garage were up in flames when Chopper five flew over the scene.

The fire had to be upgraded to a second-alarm due to the extensive vegetation overgrowth around the house.

Within a half an hour, that fire was knocked down and limited to the structure that was fully involved when units arrived.

Contra Costa Fire crews said a swift response prevented spreading the flames to the dense vegetation and neighboring homes.

There was no word yet from authorities on what caused the fire.

Thursday morning, some homeowners had a close call after a fire burned dangerously close to their Walnut Creek neighborhood before firefighters knocked out the flames.

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The fire sparked shortly after 10 a.m. Thursday morning and burned a half acre before being contained.

Chopper 5 was overhead as the vegetation fire burned a hilltop in Walnut Creek near Sutherland Drive and Walnut Boulevard.

Aerial footage showed the line of firefighters as they made their way up to the fire zone. Behind the clouds of smoke, homes were visible along the foothills.

Contra Costa Fire reported that the fire was knocked down as of about 10:45 a.m. Crews were set to remain at the scene to mop up the fire.

“Fortunately today, the weather was in our favor in this particular circumstance. Winds are pretty low, the humidities are reasonable and temperatures are cooler than normal for this particular season,” said Contra Costa County Fire Battalion Chief Bob Atlas.

The cause of the fire has not been confirmed. Walnut Creek police were also on scene speaking with people who were in the area.

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It was not clear if an arson investigation was underway in connection with the incident.