Lawmakers on Thursday called on Americans to “wake up” to what they say are the dangers posed by Chinese-owned and manufactured rail cars and buses, citing cyber and national security concerns.

The latest pushback comes in the wake of agreements between two Chinese groups and multiple U.S. cities to build public transit systems, with lawmakers on both sides of the aisle warning that such deals could compromise the security of transportation system data.

“The potential for an adversarial state actor to monitor the movements of American citizens, hack personal or government-issued devices, and collect intelligence on our military is a major security concern,” Sen. John Cornyn (R-Texas) said at a Senate Banking Committee hearing on threats posed by state-owned and operated transportation services.

“Allowing American trains and buses to become Trojan horses for these technologies on American soil is unacceptable,” Cornyn added.

Cornyn was one of the sponsors of a bill signed into law in December as part of the 2020 National Defense Authorization Act that bans the use of federal funds to purchase passenger rail cars or buses from state-owned or controlled groups.

However, a clause was included for the law to not take effect for two years, a provision Cornyn opposed.