A 20-acre brush fire alongside Highway 29 near Highway 121 Thursday closed both highways for more than two hours, creating quite a traffic mess.

The fire that started just after 10 a.m. began burning alongside the right shoulder of southbound Highway 29, just below the area where Napa's Belted Galloway cows — affectionately known as Oreo cows — wander and graze on the hillside above.

A person reporting to be a witness to how the fire started told CHP a tree branch fell into a power line, sparking the blaze. Winds were blowing strong in a north-to-south direction in the area of the brush fire when the fire began.

The fire was contained around noon, according to Napa Fire Capt. Scott Sedgley.

“The fire will not be getting any larger, but there could be hot spots that firefighters will have to mop up before they leave,” Sedgley said.

The larger portion of the fire burned the hillside south of the Oreo cows area, closer to Highway 121 that takes people from Napa towards the Carneros region and Sonoma.

Sedgley said no one was hurt, including the Oreo cows. No buildings or homes were threatened.

“The wind is what really caused the fire to spread. If it hadn’t been for the wind, the fire would have been no more than a spot of grass fire,” said Sedgley.

CHP initially closed both directions of Highway 29 from Highway 221 to Imola Avenue. Highway 121 was also closed in the area, with eastbound traffic being diverted on to Old Sonoma Road, and  westbound traffic unable to access the highway as it was closed at the Highway 29 intersection.

Golden Gate Drive was closed at Imola Avenue and also at Foster Road due to the fire. Stanley Lane at Golden Gate Drive was also shut down.

All of the roads were open to traffic by 12:30 p.m.

Later that afternoon, county firefighters responded to another small fire at the end of Green Island Road, north of American Canyon.

The fire, which burned an acre of grass, was started by a leftover campfire from Wednesday night, according to CalFire.

Because of the remoteness of the site of the blaze, firefighters were not able to reach it by engine and had to hike in.

American Canyon fire assisted.

Register staff writers Carlos Villatoro and Marsha Dorgan contributed to this story.