Teams of BART police officers, fare inspectors and agency managers converged on four downtown San Francisco stations Monday morning in the transit agency’s latest bid to crack down on fare evaders who cost the system millions.

The blitz — expected to continue for at least a few weeks — launched during the morning commute at the Embarcadero, Montgomery, Powell and Civic Center stations. Commuters, many delayed after a train struck and killed a person on the tracks at El Cerrito del Norte Station, were greeted by a handful of BART managers in neon-green vests standing inside the fare gates and a couple of fare inspectors and police officers outside. Teams were stationed at each collection of fare gates, stymieing would-be scofflaws.

The crackdown had a noticeable effect. Some people turned around at the fare gates and backpedaled to the add-fare machines; others paused to pull a ticket or Clipper card out of their pockets; and still others headed toward an alternate exit — apparently hoping to sneak out in peace without paying.

BART has for the past few years been stepping up efforts to combat fare cheats, and Monday’s action underscored how pernicious and persistent the problem has become, spreading throughout the system and among riders of all ages and economic means. Many BART riders, rattled by an increase in violent crimes, see fare evasion as a sign that the trains and stations have become places where lawlessness is tolerated.

In a statement released after The Chronicle spotted the enforcement operation and sought comment, BART officials said the effort was as much a show of force to reassure riders of the system’s safety — and of the police’s presence — as it was a targeting of fare evaders, who are estimated to cost the system about $25 million a year in lost revenue.

BART has employed a variety of strategies, with mixed success, to combat fare evasion, including locking some swing gates, building taller walls around the paid areas of stations, and creating a team of a dozen civilian fare enforcement officers who roam stations and trains asking people to prove they’ve paid. Chronicle reporters, though, have found that only a small percentage of those issued fare-evasion citations have paid the fines.

As violent crime has jumped on BART and become more visible, passengers have called for more evident police presence on trains and at stations. Alicia Trost, a BART spokeswoman, said Monday that the enforcement surge is “about expanding presence in our stations. Riders say want to feel safe and secure in our stations, and that’s what we’re giving them.”

During the blitz, all police officers and fare inspectors will have one day off each week canceled — and will work extra hours to bolster their visibility, especially in the busiest parts of the system. A BART security plan released in August said mandatory overtime and enforcement would be used intermittently as part of the system’s security strategy.

“We are taking concrete action in direct response to the concerns of our riders,” BART General Manager Grace Crunican said in a prepared statement issued after The Chronicle asked for comment. “Our riders want to see more employees on the trains and platforms and at the fare gates. This plan lets us immediately increase employee presence while we work to hire more police officers.”

In addition to the “strategic saturation,” as BART calls it, the agency plans to hire 40 more police officers — 19 of them in new positions — as well as raising walls around paid areas of more stations and installing alarms and cameras. Engineers are also working on selecting taller and tougher fare gates that would be more difficult to breach.

Toward the end of the morning commute Monday, Crunican was among the cluster of green-vested managers stationed near the fare gates.

“Good morning,” she called out as she stood inside the gates at Powell Station in an area popular among fare cheats. When she spotted a man trying to push his way through the gates without paying, she called out, “Gate!” That prompted a police officer outside to approach the man.

She directed a woman who pulled a ticket out of her pocket, while feigning confusion, to talk to a station agent. A line six deep quickly formed outside the agent’s booth. Inside the booth, as the commute slowed, an agent who did not want to give her name said it had been a busy morning.

“We had a lot of people show up at the booth saying ‘I forgot this’ or ‘I lost that’ or turning their purse upside down to show that they didn’t have any money. Uh-huh. Everybody had an excuse.”

Commuters, though annoyed by the morning slowdown, mostly seemed appreciative of the crackdown. “I like it,” called out one woman as she tapped her Clipper card and passed through the fare gates. “Everybody has to pay.”

Jordyn Christo, 19, of San Francisco, was nabbed by the police after he pushed through the gates without paying. After a long conversation with two officers, he was given a warning.

“It’s what they have to do, honestly,” he said with a shrug. “I wish there were a way for more low-income people to access public transportation and get around the city. But the enforcement is understandable. Everyone needs to be accountable for their actions.”

Michael Cabanatuan is a San Francisco Chronicle staff writer. Email: mcabanatuan@sfchronicle.com Twitter: @ctuan