VANCOUVER - Police said Friday they were acting on a tip when they raided the office of the Downtown Eastside Residents Association looking for evidence in the theft of the Olympic flag from city hall.

But the association and the Anti-Poverty Committee said the raid was a bid to discredit social activists opposing the 2010 Winter Games.

"We consider what happened last night to be an all-out attack on this organization," said Kim Kerr, executive director of the association.

"It's an organization that's been down here a very, very long time, and whose championing of a cause for people are going to end up homeless or are already homeless is well known."

He said in the association's 34 years, it has never been subjected to a search warrant.

Sister Elizabeth Kelliher, chairwoman of the association's board, said she was shocked that the police chose to focus their energy on searching the association, when they should have been helping those in need.

"I have always, from childhood up, looked to the police department for protection, for making sure our society is a just one, that nobody was treated unfairly," she said.

"How can a police department do something that they know has no relationship to the truth?"

Police said they obtained a search warrant after they got an anonymous tip about the flag's whereabouts.

Two detectives and six uniformed officers went to the DERA offices Thursday evening so they wouldn't attract any protesters.

"We have had some violent altercations in the past, so the numbers were strictly for officer safety," said Const. Tim Fanning.

The officers searched the storage locker area of the building and took a number of photographs. After an hour, they left empty-handed.

Fanning downplayed any criticism for the amount of energy the police force is putting into the missing flag.

"We follow up every criminal case as much as we can, as much as resources allow," he said. "This is something that affected a lot of people...it was very upsetting to the citizens of Vancouver."

A group calling itself the Native Warrior Society claimed responsibility shortly after the flag vanished from the lawn of city hall three weeks ago. They circulated an e-mail of masked men holding up what appears to be the flag.

After the flag's disappearance, both DERA and the Anti-Poverty Committee issued statements denying any involvement.

"Although criminal, (the theft) is an extremely courageous and powerful and inspiring act, which I fully and whole-heartedly support as does my organization," said Jill Chettiar, with the Anti-Poverty Committee.

Members of both organizations vowed not to tone down future protests.

"This organization has been here a long time and has fought for the rights of people in this neighbourhood a long time and will continue to do so as vigorously as we have in the past," said Kerr.

He said that the association was looking into legal action against the police.

The Anti-Poverty Committee has been at the forefront of protests at recent Olympic events.

The protesters say the money going towards the Olympics would be better spent to build social housing and ease poverty.

In February, protesters disrupted a ceremony to unveil the Olympic countdown clock. Anti-poverty protesters stormed the stage, shouting obscenities and pelting police with rocks, eggs and paint-filled balloons.

A few weeks later at a flag-lighting ceremony at city hall, police presence was heightened and protesters were searched before entering a fenced off area. Two people were arrested for breach of the peace.

Those there to disrupt the ceremony managed to drown out the event's speakers as well as a children's choir.