The presence of Department of Homeland Security (DHS) police officers on light-rail trains in the Twin Cities provoked unease among some passengers Wednesday. Several took to Twitter to express their dismay.

But Metro Transit said the DHS officers are part of a Visible Intermodal Prevention and Response (VIPR) team working with its own police force to help ensure security on public trains and buses. The VIPR officers do not engage in any enforcement actions, and have worked with the department for “more than a decade,” said Metro Transit spokesman Howie Padilla.

After DHS officers were spotted on the Green Line Wednesday, some passengers tweeted their alarm, especially as fear spreads locally regarding possible immigration roundups. This prompted Metro Transit to tweet an assurance that their officers “do not do immigration sweeps.”

Despite that explanation, several passengers wondered why the DHS officers were carrying plastic handcuff wristlets, and why their presence was necessary in the first place.

One tweeted that it was “spectacularly ill-considered. Perhaps we should get the SEALS to monitor polling places, too.” Another called the practice, “Gross. Please keep Feds off our public transit.” Another noted, “You need to seriously rethink this policy and do a meeting with the community.”

The DHS officers accompanied Metro Transit police officers who were conducting routine fare checks. Over the years, other federal officers, including those from the Federal Air Marshal Service, have partnered with the force, Padilla said.

The collaboration provides “an opportunity to strengthen partnerships so that Metro Transit officers can work with those agencies more seamlessly in the event of an actual emergency or during times of heightened security like the upcoming Super Bowl,” Metro Transit said on its website.