SAN FRANCISCO -- The busy evening commute out of downtown San Francisco gave way Monday to a chaotic cat-and-mouse game between police officersand roving protesters who lashed out at the transit agency for temporarily shutting down underground cellular phone service last week.

BART closed all four downtown San Francisco stations - Civic Center, Powell, Montgomery and Embarcadero - soon after the protest began at 5 p.m. Officers in riot gear blocked entrances as many train riders fumed on the sidewalks and tried to figure out how to get home. All stations were reopened by 7:30 p.m.

Muni Metro stations at the same locations were closed in tandem with the BART stations.

BART's action last Thursday - which ignited an international debate about technology, free speech and public safety - was an effort to diffuse an antipolice demonstration. But it spurred an even larger protest Monday that was organized online by a loose-knit band of computer hackers known as Anonymous.

Trains continued to run through the stations, only allowing passengers to exit. Outside, protesters carried signs and chanted, while some - at the urging of Anonymous - wore T-shirts spattered with fake blood and creepy Guy Fawkes masks popularized by the graphic novel and movie "V for Vendetta."

At a brief news conference after service was fully restored, BART spokesman Linton Johnson said, "Tonight our customers are angry and frustrated."

Police reported no arrests and no injuries.

Closing the stations

The station closures began at 5:25 p.m., when protesters were ejected from the Civic Center Station after at least one blocked a door of a Dublin-Pleasanton train for two minutes as others chanted "No justice, no peace." The train continued east, and police issued a dispersal order.

"Once we got to a situation where the BART platform was unsafe, we cleared the station," said BART Deputy Police Chief Daniel Hartwig.

He said cell service was never switched off. "The bottom line with cell service is that it's always in the game plan, but we chose not to utilize that resource tonight," Hartwig said. "Once we read the dispersal notice and they complied, we didn't feel like any other actions were required."

Demonstrators then began marching toward the other stations, prompting BART to close them, one by one, as people affiliated with the hacker group gloated online through Twitter. At one point, near the Embarcadero Station, protesters blocked Market Street, but quickly complied with police orders to clear out.

Some transit riders were infuriated. Jennifer Cohn, an attorney who works downtown, arrived at the Civic Center Station at about 6 p.m. with her two sons, ages 3 and 4, after picking them up from day care. She was trying to get home to the Glen Park neighborhood.

With the station closed, she tried to catch a cab, but they seemed to be avoiding the area.

"This is an outrage. We just want to get home," Cohn said. "I don't really see why they should be shutting down the stations. If they have an issue with BART, they should go to BART headquarters."

But Ryan Bell, 25, of San Jose yelled to sullen-faced pedestrians, "What's a bigger inconvenience, missing your train or getting shot by a BART cop?" Other protesters held phones with cut cords while repeating "Can you hear me now?"

Johnson, the BART spokesman, said earlier Monday that the agency had the right to cut cell phone service Thursday because transit riders "don't have the right to free speech inside the fare gates." He said passengers' safety was threatened by protesters upset over a BART police officer's fatal shooting of a knife-wielding man on July 3.

"We're in the business of transporting people from point A to point B safely," Johnson said. "We were forced into a gut-wrenching decision on how we were going to stop (the possible Thursday protest), given the propensity of this group to create chaos on the platform."

Genesis of the protests

Activists angered by the police shooting of Charles Blair Hill disrupted service during a protest July 11 that started at Civic Center Station and spread to the 16th Street Mission and Powell Street stations. BART closed all three stations for varying lengths of time.

BART shut down cell service Thursday at four downtown San Francisco stations, Johnson said. The agency did not jam cell signals, which is illegal, but shut off the system - which Johnson said is allowable under an agreement with several major phone service providers that pay rent to BART.

Lynette Sweet, a member of BART's Board of Directors, said Monday that she opposed any further disruption of cell service and would seek to bring the issue before the board for a vote.

"This is one where we can almost say we're stuck on stupid," Sweet said. "We put ourselves on the radar screen for no good reason. This is a country that champions civil liberties all the time. So why would a transit agency take it upon themselves to trample on civil liberties?"

The Federal Communications Commission is looking into BART's action. In a statement Monday, spokesman Neil Grace said, "Any time communications services are interrupted, we seek to assess the situation."

The protest came after the hackers breached a BART website Sunday and released personal information from more than 2,000 customers. Johnson said the FBI was investigating the hack attack.

BART serves San Francisco, San Mateo, Alameda and Contra Costa counties, with about 350,000 boardings a day.