Fewer than a quarter of what appear to be surveillance cameras inside BART train cars are real and functional, transit agency officials said Tuesday.

BART detailed exactly how many of its train cameras actually record footage in response to a public records request that The Chronicle filed after revealing the agency had been relying for years on scores of decoy cameras to fool criminals and commuters.

After acknowledging that most of the security devices on trains were dummies — but defending the strategy — BART officials said they would phase out the fakes and replace them with working cameras at a cost of $1.4 million.

Each train car now has a set of four devices that appear to be cameras, mounted to the ceilings.

But BART said Tuesday that just 22.6 percent of the cars had working camera systems. The agency said 70 percent of cameras were fakes, and that others were either broken or inactive.

The Chronicle revealed the decoy program after learning that BART had failed to film the Jan. 9 fatal shooting of a man aboard a train at the West Oakland Station.

The slaying of 19-year-old Carlos Misael Funez-Romero of Antioch remains unsolved despite a $10,000 reward. Four days after the killing, BART police released photos of the suspect that were taken by station cameras as he entered the system in Pittsburg and as he left the West Oakland Station.

Investigators have discovered that the suspect and victim both boarded at the Pittsburg/Bay Point Station, 30 miles away, after riding the same Tri Delta Transit bus to the station.

The men — who were captured by cameras on the bus — had some sort of “interaction” that apparently continued until the 7:40 p.m. shooting, BART said. But the relationship between the men, if any, as well as the motive for the killing, remain unknown.

The suspect, a tall, thin black man with close-cut hair, appeared to be wearing a dark green jacket with a hood, a backpack, jeans and beige work-style boots.

The use of dummy cameras is common in private security but unusual among transit systems. And although BART’s use of the decoys was an open secret at the agency, many officials, including some board members, were unaware of it.

BART is replacing its entire fleet of trains, and officials said every car in the new fleet will be equipped with cutting-edge cameras producing footage that can be watched live from a central monitoring station. Those cars are expected to arrive between 2017 and 2021.

Also Tuesday, BART said it did not rely on decoy cameras outside of its train cars.

It said that 10 stations had extensive camera systems and that those stations were each outfitted with between 68 and 85 cameras. All the cameras are believed to be functional, officials said. An additional 16 cameras are mounted at “sensitive” sites around the BART system, officials said.

BART did not provide the exact location of all cameras, citing concern that the information could aid terrorists. It also did not give the age of every camera, citing a lack of accurate records.