It may not match the anti-crime surveillance of London, but a network of outdoor cameras in downtown San Francisco continues to expand as the city deals with a rash of property crime.

What started as a pilot program with six privately owned cameras around Union Square has morphed into a coordinated web of 350 cameras that share footage with the police, where officials would love to see the partnership grow.

The Union Square Business Improvement District started the security camera program in 2012 and has since raised more than $3 million in grant money while outfitting about 40 property owners with cameras, said Karin Flood, executive director of the organization.

All the footage funnels into a control room at Geary and Powell streets, where the feeds aren’t monitored in real time but can be supplied to police upon request, after a crime has been reported.

Flood said her organization received more than 750 police requests for footage from February 2015 to March 2018. She said city prosecutors, public defenders and even private citizens have also sought video and are given access “in most cases.”

She estimated the cameras have played a role in 225 arrests in the Union Square and Tenderloin areas, but that couldn’t be verified. San Francisco police don’t keep data on their use of camera footage to solve crimes.

“The police have really come to rely on us for that footage,” Flood said. “We have a network of cameras, so you can really piece an incident together better and tell the whole story — it’s not just an individual shot.”

The Union Square group, which spans 27 square blocks, received grant funding from the Silicon Valley Community Foundation. The district works with the vendor Applied Video Solutions and dedicates staff members who manage the camera program and coordinate with police.

Flood said the group has passed along $350,000 in grant funds to the Central Market and Tenderloin community benefit organizations to better cover the Tenderloin neighborhood.

Sgt. Michael Andraychak, a city police spokesman, said video provided by private parties routinely captures valuable images of suspects or crimes as they occur.

“I can tell you that I see several crime alerts every day that include either still photos or video links,” Andraychak said. “Surveillance cameras are becoming more and more common in San Francisco and in our daily lives.”

San Francisco once envisioned a publicly funded network of anti-crime cameras.

Then-Mayor Gavin Newsom started an expensive program in 2005, installing cameras in some high-crime areas, but it was hampered by weak oversight and equipment that delivered low-quality footage, according to University of California researchers and reporting by The Chronicle. Few arrests were made, and privacy advocates also raised concerns.

In recent years, several cities have developed partnerships in which merchants or residents put up cameras while working with police and sometimes taking advantage of grants.

Supervisor Jane Kim, who represents the Tenderloin, said a fair balance has been struck with the Union Square initiative.

“While I’m very mindful of privacy concerns, especially in today’s tech-filled world, residents deserve to feel safe in their neighborhoods,” said Kim, a mayoral candidate. “My understanding is that camera footage in the Tenderloin has been limited to specific incidents and has actually led to arrests in multiple homicides.”

The shared footage is designed for aiding police with serious crimes, not “quality of life” issues, Flood said. The cameras, she noted, can help solve auto break-ins in a city that saw more than 31,000 reported last year, claiming the highest per-capita break-in rate of any big city in the state.

Flood said the Union Square Business Improvement District now works closely with the Sutter-Stockton parking garage — a hot spot for smash-and-grabs — and has helped to install cameras on both the exterior and interior of the building.

“Their numbers are coming down,” she said of thefts in the garage, “so that has been a success story.”

Fisherman’s Wharf is among neighborhoods where the surveillance partnership could expand, said Troy Campbell, executive director of the Fisherman’s Wharf Community Benefit District.

“It’s something we are considering at this time,” he said. “Right now we are trying to find out what the cost is going to be.”

The financial incentive for business owners is clear: In Union Square, the owner must pay for 10 percent of the camera costs, with grant money covering the rest. For Fisherman’s Wharf merchants, Campbell said, these cost-sharing details still need to be hashed out.

Nevertheless, he said there is a growing desire among business owners to contribute to solving crimes using modern technology.

“There are a lot of cameras now, but they are not facing the street, so you are not going to see what car they got into,” he said. “A lot of cameras are older and are not the high-definition ones that can pick up more detail.”

Flood said cameras are generally best placed 10 to 15 feet off the ground. She declined to provide a list of their locations.

“We don’t like to publicize,” she said. “We don’t want the bad guys to know.”

Ted Andersen is a San Francisco Chronicle staff writer. Email: tandersen@sfchronicle.com Twitter: @ted_d_andersen