Oakland police are investigating City Councilwomen Jean Quan and Rebecca Kaplan for their decision to join a human line that blocked police from moving up Broadway during the demonstration Thursday night.

"The whole civil unrest incident is still under investigation," said Oakland police spokesman Jeff Thomason, who added that additional arrests are likely.

"Regarding council members Quan and Kaplan, they are not exempt from this," he said.

The councilwomen, who are both running for mayor, say they were merely acting as peacekeepers, trying to calm a tense situation.

The event in question began on Broadway near City Hall a few hours after a Los Angeles jury found former BART police Officer Johannes Mehserle guilty of involuntary manslaughter for fatally shooting Oscar Grant, an unarmed train passenger. About 1,000 people gathered downtown after the verdict was announced.

When police began clearing the street and threatening demonstrators with arrest, tensions began to rise.

Quan and Kaplan helped to form a line that separated the protesters from getting to the cops - a line that also stopped the advancing police officers.

Quan, who as chairwoman of the council's budget committee has been the subject of robo calls by the police union over the layoffs, said through a City Hall aide that her goal was "to keep things peaceful and help keep the police from overreacting and equally keep the crowd from overreacting."

Kaplan said their actions "helped prevent things from escalating."

The cops see it differently.

"They were encouraging people not to listen to us," said one officer who was on the line. "At one point, Kaplan was even giving a TV interview while her arms were locked, blocking us.

"If we had needed to go into the crowd, we shouldn't have to worry about going through a council member first," the cop said.

Meanwhile: Oakland's police tab for responding to Mehserle's involuntary manslaughter verdict will top $1 million, according to preliminary reports from City Hall. And that doesn't include the costs incurred by the 15 other agencies that sent officers to help.

In addition to overtime costs, Oakland paid for setting up two police staging areas and also feeding hundreds of cops from other departments.

For example, the California Highway Patrol sent 400 officers from as far away as Fresno.

Oakland City Administrator DanLindheim and other officials have privately met with BART General Manager Dorothy Dugger to ask the transit agency to contribute to the city's mounting tab.

BART spokesman Linton Johnson said, however, that it is unlikely BART would pay for any of the mutual aid, though the agency is planning a $25,000 donation to one of the community groups that hosted anti-violence rallies.

Rent free: San Francisco Planning Director John Rahaim has been hit with a $1,000 fine by the city's Ethics Commission for not reporting the free use of a condo owned by the father of one of his employees.

The worker, Kelley Andur, was later promoted to director of neighborhood planning.

Rahaim moved into the condo when he was left homeless after his partner, Lance Farber, started a fire in the historic fire chief's house. The couple were staying there while shopping for a permanent home.

Farber was ordered to pay $50,760 in damages and went into substance abuse treatment. He died earlier this year.

After the fire, Rahaim took up temporary residence in the unoccupied condo.

"I offered to pay rent," Rahaim said, "but they wouldn't take it."

Rahaim eventually reported the free condo on his annual statement of economic interest form, but it was still a violation of the city's $390 gift limit.

Into the arena: San Francisco State University professor and CBS-5 political analyst Joe Tuman has joined the list of candidates running for mayor of Oakland.

"This town is in crisis," Tuman said. "We need someone who will address the major structural problems and make difficult decisions. And that may mean making choices that career politicians worried about re-election simply will not make."

Tuman, a 25-year Oakland resident, said that he is the only one running who is not a career politician - so he fit the bill.

Day Tripper: KTVU reporter Rob Roth was in Golden Gate Park for his son's baseball game on Saturday afternoon when he glanced up and saw Paul McCartney riding up the bicycle path. (He wasn't wearing a helmet.)

"Game going OK?" McCartney called out.

"Yeah," Roth said. "You think you might want to sing the 'Star-Spangled Banner'?"

"I'm afraid I can't right now," the British-born McCartney called back as he pedaled onward, followed by an unidentified woman and a contingent of security.

EXTRA! Catch our blog at www.sfgate.com/matierandross.