Police are looking for a man who held up a 7-Eleven store early Wednesday morning, threatening the clerk with a 12-inch knife, according to police.

The robbery happened at 2:30 a.m., at the convenience store on Sierra Avenue.

The clerk was not hurt, Napa Police Sgt. Don Honey said.

The robber took money from the cash register and ran from the store, Honey said. "He was last seen running toward Harkness Avenue."

Officers responded, search the area, but came up empty-handed.

The robber is described as a white male, in his 20s, wearing a black-hooded sweatshirt.

Anyone with information about the robbery is asked to call the Napa Police Department at 253-4451.

Domestic violence arrest

A verbal argument over finances turned ugly and landed a Napa woman in jail.

On Tuesday afternoon Adriana Ortega, 21, was riding in a car with a male driver on Highway 29, near Yountville. The pair were arguing and Ortega allegedly punched the victim in the mouth, sheriff's Capt. John Robertson said.

The victim stopped the car, got out and went to the roadside telephone call box and called sheriff's deputies, Robertson said.

Ortega drove off in the car, heading for her Napa home. She was arrested later at a residence in the 1200 block of Yajome Street on suspicion of felony domestic violence.

Blown transformer torches grass

A transformer blew up on Tuesday afternoon igniting a grass fire that scorched a quarter-acre of grass in American Canyon.

The small blaze happened at the city of American Canyon's water tank site on the top of Oak Hill, off Theresa, American Canyon Fire Chief Keith Caldwell said.

Downed power lines knocked out power to the city pumping station and one nearby business, Caldwell said.

Ground breaking ceremony set

American Canyon public safety is getting new digs.

Ground breaking ceremonies for the 22,000-square-foot fire and police facility is set for 10 a.m., Saturday at Donaldson Way and Vinegate Way. The public is invited. Refreshments will be served.

The state-of-the-art building will be constructed on 2.25 acres.

Access to the site is from Silver Oak Trail, north of American Canyon Road at the intersection of Broadway. Signs will be posted.