The U.S. Postal Service said on Monday it would tighten safety requirements for contracted trucking providers by phasing out non-domiciled commercial drivers who have not been vetted by the agency.

The announcement followed the U.S. Transportation Department's emergency regulation to restrict commercial driver licenses to immigrants or non-U.S. citizens after a fatal crash in Florida and a government audit.

USPS, which moves 55,000 truckloads a day, said it would monitor contractor performance and safety data as part of its efforts to reduce accidents across its network.