OAKLAND — Alameda County has sold for $9.56 million a vacant office tower it owned in the heart of downtown Berkeley, setting in motion even bigger real estate rumblings in Oakland.

County officials plan to use the proceeds to remodel another vacant office tower in downtown Oakland so that about 400 county workers can move in. That, in turn, will allow the county government — one of Oakland’s top employers — to empty and unload four grim public buildings guarding a coveted gateway to Jack London Square.

“What we’ve been trying to do as a county is free up those blocks for other potential development,” said Aki Nakao, director of the Alameda County General Services Agency.

A “serendipitous event” three years ago helped pave the way for the workplace shuffle, Nakao said. Seeking to foreclose a private realty firm’s $47 million delinquent loan, Bank of America in late 2010 seized two office buildings: the seven-story tower at 2015 Shattuck Ave., in Berkeley; and the eight-story former federal building at 1111 Jackson St., in Oakland.

The realty firm had bought the properties, including a parking lot near the Oakland building, for $61.5 million in 2007. The value had dropped to $26 million three years later when the foreclosed buildings went on sale in a public auction on the steps of the Rene C. Davidson Courthouse. Alameda County was the winning bidder.

But it was the Oakland property more than the Berkeley one that interested county officials. Built by the state in the 1960s and refurbished after being damaged in the Loma Prieta earthquake, the gleaming white building at Jackson and 11th streets sits around the corner from Alameda County’s administrative headquarters near Lake Merritt. It was most recently a federal hub, home to regional branches of the Social Security Administration and other agencies.

“The vision we have is to make the space within 1111 (Jackson) more contemporary, a more open office, and not so much the old-fashioned cubes,” Nakao said.

Most of the Alameda County Probation Department and a segment of the county Social Services Agency plan to move there as early as next year, vacating two stark mid-20th century buildings the county owns at 400 and 401 Broadway, near Interstate 880 on the route to Jack London Square.

The county has had a presence on that Oakland block since the late 19th century, when it built a domed, ornate courthouse that was later demolished. More recently, the area has been eyed for condo development or a new convention center.

Also planning to move out from its historic home on 4th Street off Broadway will be the Coroner’s Bureau. The coroner’s office, and a nearby county public health laboratory on Fifth Street, are both moving to an office park on Peralta Oaks Court in the Oakland hills.

Less clear is the future of the recently sold Berkeley office tower, a 30-year-old building at the busy corner of Shattuck and University avenues.

Alameda County never occupied the building after buying the foreclosed property. It is vacant except for a ground-level restaurant and store.

The Peralta Community College District considered buying it to make more room for its Berkeley City College. Also interested was the ever-expanding UC Berkeley, which once leased some of the upper floors. Both schools backed out earlier this year.

“We just took a look at it and didn’t think it would be cost-effective,” said Peralta spokesman Jeff Heyman.

The Alameda County Board of Supervisors formally accepted a $9.56 million written bid from Ten Capital Real Estate LLC at the county’s regular meeting Tuesday, completing the sale after no one else said they wanted it.

“Congratulations, you just bought yourself a big piece of property in the city of Berkeley, whoever you are,” said Supervisor Scott Haggerty.

A San Francisco-based partner at the investment management firm, David Smith, said this week he was not ready to talk about any plans for the seven-story Berkeley building.

Matt O’Brien covers Alameda County. Contact him at 510-208-6429.