The Transportation Security Administration has quietly yet vastly expanded its reach to sporting events, music festivals, rodeos, highway weigh stations and train terminals, according to the Star-Tribune.

TSA and local law enforcement officials say the Visible Intermodal Prevention and Response squads – dressed in bulletproof bets and performing random security sweeps to prevent terrorist attacks at transportation hubs across the U.S. – are a critical component of the nation’s counterterrorism efforts. Some members of Congress, auditors at the Department of Homeland Security and civil liberties groups are sounding alarms, however. The teams are also raising concerns among passengers who call the sweeps unnecessary and intrusive, the article reports.

The DHS auditors are asking about the teams’ training protocols and deployment based on actual security threats. Civil liberties groups say the VIPR teams have little to do with the agency’s original mission to provide security screenings at airports and that, in some cases, their actions amount to warrantless searches.

TSA officials respond that the random searches are “special needs” or “administrative searches” that are exempt from probable cause because they further the government’s need to prevent terrorist attacks, the article says.

The VIPR teams were created in 2005, in part as a reaction to the Madrid train bombing in 2004 that killed 191 people. The program now has a $100 million annual budget, increasing to several hundred people and 37 teams last year (up from 10 teams in 2008).