SAN FRANCISCO (KPIX 5) — A network of security cameras in San Francisco is getting bigger.

The first cameras in this network were installed in 2012 and since then there’s been mixed reaction.

Some say it’s an invasion of privacy, but others say it’s a necessary step to fight crime.

In San Francisco’s quintessential Union Square, cable cars carry excited tourists and sidewalks are packed with shoppers, but watching it all from above are hundreds of high definition cameras.

Karin Flood with the Union Square Business Improvement District said, “What makes a difference really is, it’s not an individual camera, it is a network of cameras so we’re really able to help the police to tell the whole story.”

There are more than 350 cameras in all. The video goes onto servers where it’s stored for 30 days, then erased.

“We’re not actively monitoring these cameras. We really just pull footage after the fact,” Flood said.

The string of cameras captured the runaway double decker tourist bus that barreled down three city blocks out of control in November of 2015, which left 20 people injured.

The cameras also helped police break the case in the Rainbow Crew, a band of shoplifters who are accused of stealing more than $1 million in merchandise from Union Square stores.

“The cameras are being used for serious crimes. We’re not watching some of the quality of life instances that happen on the street,” Flood said.

Tourists we talked to said they like knowing the cameras are there.

Annette Edmunson, a tourist from England, said, “You don’t really know they’re there. So, if you’re not doing anything wrong, then you’ve got nothing to worry about.”

Terry West, a tourist from Australia, said, “I think it’s a great idea and I think it should be encouraged in all cities.”

The camera network around Union Square has been so successful in providing evidence to police, it’s now expanding to neighboring districts in Central Market and the Tenderloin.

San Francisco City Supervisor Jane Kim said, “Our residents are tired and fed up with the low level crimes that are occurring in their neighborhood on a daily basis.”

Supervisor Kim says she has talked with Tenderloin residents about their privacy concerns.

“As long as the video cameras, again, are not in the hands of government, but held by private property owners, and only given to us in the case of a criminal incident, our residents have been very comfortable,” Kim said.

All of the cameras are on public streets and sidewalks where, according to the law, there is no reasonable expectation of privacy.