The owner of a burning suburban St. Louis landfill near buried radioactive waste has agreed to new measures meant to slow and help monitor the underground blaze, a U.S. Environmental Agency administrator said Thursday.

While stressing there's no evidence the nagging fire has greatly spread, regional EPA chief Mark Hague told reporters on a conference call that Republic Services will install temperature monitors, as well as cooling loops or heat extractors designed to help control the fire's temperature.

The company also will broaden a plastic cover over the landfill, partly to suppress odors and to block out oxygen that could feed the blaze, Hague said.

As part of the agreement, the EPA said, Republic must submit plans for the cooling system within 30 days and finish the work four months after construction begins.

The smoldering Bridgeton Landfill west of St. Louis is adjacent to the West Lake Landfill, where Cold War-era nuclear waste was buried four decades ago. Hague said the moves made public Thursday were precautionary.

"Ultimately, the goal is to get a proposed final remedy in place this year," he said.

In December, the EPA ordered the installation of an isolation barrier to make sure the underground fire — the cause of which is unknown — does not reach the nuclear waste at West Lake, which was declared a Superfund site in 1990.

Republic said in a statement Thursday that "we have been ready to put these protective measures in place for some time, and we remain committed to working with the EPA on the implementation of an isolation barrier" between the fire and the radioactive waste.

Hague said the actions announced Thursday were months in the making and "completely independent" of a federal judge's decision two days earlier to send the state of Missouri's environmental lawsuit against Republic back to a St. Louis County court.

Missouri Attorney General Chris Koster sued Republic in 2013, alleging negligent management and violation of state environmental laws. The landfill often creates an odor so strong that many residents say they are often forced to stay indoors.

Last October, the company pushed to move the lawsuit to federal court, arguing that Koster's office was seeking to assert state control over radioactive material under federal jurisdiction.

Koster called the move a few months before a trial date a stalling tactic.

The judge ruled Republic had injected a federal question into an otherwise state-law claim.