VERNON, Calif. (AP) — Members of Congress asked the federal government to help clean up toxic lead contamination from a former battery recycling plant outside Los Angeles.

Sens. Dianne Feinstein and Alex Padilla joined Long Beach Rep. Robert Garcia in appealing Thursday to the Environmental Protection Agency for help with the former Exide Technologies plant cleanup, the Los Angeles Times reported.

The plant in Vernon is the source of the largest and most costly cleanup in California history. The letter by the three Democrats said EPA should designate the plant a Superfund site to get the necessary funds to cleanup lead from as many as 10,000 properties.

The letter cited a Los Angeles Times report that said research showed soil in the yards of 73 of 93 remediated homes had lead concentrations over the state health limit. In 22 of those homes, at least one sample exceeded the threshold fivefold.

The state is currently overseeing the $750-million remediation effort and has, so far, spent more than $336 million to remediate nearly 4,400 properties.

"It is clear that only the federal government has the capacity to resolve this crisis," the lawmakers wrote to EPA Administrator Michael Regan. "We believe the severity of the crisis, the failure of past remediation efforts to create healthy communities, and the risk to public health requires assistance from the EPA and the resources available under the Superfund program."

The plant operated near the Los Angeles River for nearly a century and was cited by local, state and federal officials for violating hazardous waste laws by emitting too much lead and arsenic around the plant and on highways where its trucks traveled. Exide Technologies acquired the plant in 2000 and ran it until 2015.

Exide, which has said it didn't contaminate surrounding neighborhoods, has not been held responsible because it filed for bankruptcy in 2020.

A spokesperson for Democratic Gov. Gavin Newsom said bankruptcy courts had "let Exide off the hook" and the state would welcome EPA assistance.

"We appreciate this support for the state's request to designate the Exide facility and surrounding community as a Superfund site, which will result in even more funding to support cleanup," spokesperson Anthony York said. "The state will continue to pursue all avenues to advance these efforts and protect public health."