As a Green Line light-rail train edged away from the Government Center stop in downtown Minneapolis one recent Friday evening, a haze of cigarette smoke wafted through the car.

The identity of the puffer wasn’t clear, and passengers this time pointedly ignored the increasingly common offense — a misdemeanor that could result in a citation and up to a $300 fine.

In 2018, Metro Transit received some 1,800 complaints about people smoking tobacco, marijuana and e-cigarettes on trains and light-rail platforms. The problem appeared to flare up toward the close of the year and continued into 2019 — the transit agency has fielded nearly 600 complaints so far this year.

Beginning this week, Metro Transit police officers in plainclothes have surreptitiously parked themselves on both Green and Blue line trains to ferret out smokers.

“It’s not going to be every day or all day long,” said A.J. Olson, Metro Transit’s interim police chief. Undercover officers will check out trains based on days and times determined to be popular among smokers — generally midafternoon and on the Green Line, which links the downtowns of Minneapolis and St. Paul.

But the police-led crackdown has drawn concern from transit advocacy groups.

Jessica Treat, executive director of Move Minnesota, worries people of color will be profiled in the enforcement effort. “Yes, smoking on the train is not a good thing, but is policing the way to handle it?” she asked.

Plus, Treat said, people cited for smoking may get caught up in the criminal justice system for a minor offense.

“When police confront transit riders, the situation can escalate,” said Amity Foster, spokeswoman for the advocacy group Twin Cities Transit Riders Union. “This is an overreaction to an unpleasant but nonviolent citation. There must be a better, civilian approach.”

Transit agencies across the country face the same struggle with passengers smoking on trains, according to the American Public Transportation Association (APTA). The Twin Cities isn’t unique in that regard — although Olson concedes recent harsh weather may have drawn more smokers to the train’s relative comfort.

The broader concern is whether these so-called nuisance issues — smoking, loud music, sleeping on the train — discourage people from using public transportation.

“Do these behaviors deter people?” Olson said. “I don’t know whether it does or doesn’t, but light-rail [ridership] numbers continue to grow.” Ridership on both the Green and Blue lines was up last year, by 5 percent and 4 percent, respectively. Still, he said, “While we run a very safe system, people need to feel safe.”

The problem doesn’t seem to draw complaints from bus passengers. That’s because bus drivers “say, ‘Please don’t smoke on the bus,’ ” Olson said. Light-rail operators don’t know whether people are smoking aboard unless someone alerts them through the emergency intercom located in each car.

Polly Hanson, APTA’s director of security, risk and emergency management, notes that smoking is not only a nuisance — it’s a safety issue.

“Cigarettes are combustible,” she said. “Newspapers, trash left on the train could catch fire.”

Some transit users say smokers should be politely confronted. Others are a bit fearful of that approach. Some say the easiest way to avoid smokers is to switch to a different car at the next stop.

Minneapolis resident Mark Snyder said he’s asked Green Line smokers to stop. “The most recent cases were on the same day about a month or so ago,” he said. “One was in the morning, and that person took exception to me asking him to stop and tried to intimidate me by yelling at me.”

“The second case was during the evening commute, and this man was older and alone,” Snyder said. “Other passengers joined in with me in asking him to stop, and I expect that was why he cooperated and put his cigarette out.”

Olson isn’t a fan of passengers confronting smokers. Instead, he urges them to report the offense by using the Metro Transit smartphone app or website, or texting the safety line at 612-900-0411.

Even if police can’t get to the train in time to enforce the no-smoking rule, the dates and times of the complaints help pinpoint when enforcement should occur, Olson said.

“We already know [that] when uniformed officers are on the train, nobody smokes because they know better,” he said. “If there’s a plainclothes officer, they can address the issue right when it happens.”