SAN FRANCISCO -- Arson investigators were reviewing surveillance video Thursday to try to identify the vandals who started a small early morning fire at the Chinese consulate here.

Someone threw flammable liquid on a metal garage door at the back entrance to the consulate offices and set the door ablaze, authorities said. The door was charred in the 4 a.m. incident. No one was injured and no arrests have been made.

A witness called authorities saying a burning device was hurled at the building and that they reportedly "heard a bang and saw some flames." Police were told two people were also seen running from the scene.

Sgt. Steve Mannina, a San Francisco police spokesman, said two people were seen running from the building around the time of the fire. Investigators were looking into whether up to four people were involved in setting the fire, with one or two serving as lookouts, Mannina said.

A motive wasn't immediately known.

Security cameras are posted on the side of the building. Police tape cordoned off the area around the part of the building where the incident took place, but the building was open for business Thursday morning.

The Chinese government has been the target of recent protests in San Francisco by activists calling for an end to China's heavy handed rule over Tibet. Protesters also have gathered to voice their opposition to the Olympic torch making its way through the city next month on its path to the Beijing Games. San Francisco is the only stop for the torch in North America.

Later in the day, members of the Bay Area Tibetan community Thursday urged San Francisco officials to include mention of human rights concerns in China during the city's April welcome of the Olympic torch.

About 100 people rallied outside City Hall Thursday afternoon, waving Tibetan flags and chanted "Free Tibet!" "Stop the killing!" and "Stop the torture!" more than a week after peaceful protests begun by Tibetan monks reportedly escalated into riots in Tibet's capital, prompting Chinese authorities to impose stricter security measures throughout the region.

Estimates of the number of people killed in the Tibet crackdown have varied widely.

When asked about the incident at the Chinese consulate, organizers of the protest denied any involvement and condemned the action.

"We have nothing to do with it," said Tenzin Dasang, president of the Bay Area's Tibetan Youth Congress, at the City Hall rally. He condemned the incident, saying, "We are completely for non-violence."

Dasang said it is an emotional time for the Tibetan people, including those now living in the Bay Area, whose numbers he estimated at about 1,500.

Dasang said Tibetans have "zero autonomy" under Chinese rule. "Tibetans have the right to choose their own future," he said.

"We have to stick with our non-violence approach," Dasang added. "That is the only way we will gain support from the international community, and it is the only way to resolve a problem."

Rally organizers also held a candlelight vigil around City Hall at 7 p.m., calling on the city to show support for human right and freedom of speech, Dasang said.

A resolution introduced by Supervisor Chris Daly was considered before Thursday afternoon's meeting of the board's City Operations and Neighborhood Services Committee.

The largely symbolic resolution calls for Mayor Gavin Newsom "to express his concern regarding the recent human rights atrocities in Tibet" when the Olympic torch is in San Francisco April 8 and 9 and to urge the Chinese government "to genuinely comply with the principles of tolerance and respect as symbolized by the spirit behind the Olympic games."

The resolution also seeks to eliminate any restrictions on where protests of the Olympic torch passing in San Francisco may take place.

The resolution would further honor the Tibetan Freedom Torch and the Global Human Rights Torch Relay, also due to make stops in San Francisco this year.