Hackers broke into the Bay Area Rapid Transit (BART) system Web site, leaking information on BART police. But this time Anonymous did not claim responsibility for the act.

The attack had put the Web site, BARTpoa.com, offline releasing full names, e-mail addresses and passwords of the police officials through a Web site.

"These people are criminals, and we're going to forward this information to the FBI," the BART union president, Jesse Sekhon, told the San Francisco Chronicle.

"These people need to be brought to justice. They can't be terrorizing people."

The hack attack was in retaliation to the shutting down of the wireless services in San Francisco subway stations, last week, which had triggered a hack attack on Sunday and a gathering on Monday forcing BART to shut down four stations.

After the previous attack on BART’s marketing Web site, leaking data of more than 2,000 users, Anonymous had said in a statement, “BART has proved multiple times that they have no problem exploiting and abusing the people. We are Anonymous, we are your citizens, we are the people, we do not tolerate oppression from any government agency.”

The American Civil Liberties Union of Northern California said in a blog post last week that: "Shutting down access to mobile phones is the wrong response to political protests, whether it's halfway around the world or right here in San Francisco. You have the right to speak out. Both the California Constitution and the First Amendment to the United States Constitution protect your right to free expression."

After the leak of police information, Anonymous tweeted: “People who are against anonymous know they can do things under the name 'anonymous' and never be questioned. This is anonymous, denied.”

“The leak today of BART officer data could be the work sanctioned by those who truly support anonymous, or agent provocateurs. Stay skeptical,” posted Anonymous, without directly claiming any responsibility.

Not every member of the loosely organized collective takes part in every action, and there is no one who commands the group or can speak on its behalf.

But a hacker who identified herself as “Lamalin_5mg” offered the link to the leaked police data, claiming it took her less than four hours to crack the BART site.

An Anonymous supporter called Crappy Tires argued, "There are really no leaders in the group, but some people did tell her that she should not have done it.”