A group of California Democrats on Monday pressed the EPA’s internal watchdog to investigate whether the agency has retaliated against their state for political reasons, including by threatening to withhold federal funds for multiple transportation projects.

EPA Administrator Andrew Wheeler threatened in a Sept. 24 letter to the California Air Resources Board, the state’s air agency, to withhold federal funding for highway projects if local regulators did not implement plans, known as “state implementation plans,” or SIPs, to improve air quality.

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In a letter Monday to Charles Sheehan, the EPA’s deputy inspector general, House Democrats requested that the IG office scrutinize whether Wheeler’s letter and its threats “are a result of undue political influence” at the agency.

Seven California Democrats — Reps. Doris Matsui, Nanette Barragán,  Jerry McNerney, Anna G. Eshoo, Tony Cárdenas, Scott Peters and Raul Ruiz — sent the letter.

Under President Donald Trump, federal agencies including the EPA have sparred with California over transportation, energy and environmental issues. The threat to hold back funding was the latest in a string of jabs the two parties have exchanged.

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Also in September, the EPA and the Transportation Department moved to rescind California’s long-standing authority to set its own limits for vehicle emissions. California Attorney General Xavier Becerra, a Democrat, sued the next day. And in May, the Trump administration pulled back $929 million for a high-speed rail project.

The president has also railed against California cities over homelessness and what he claimed were environmental violations and said the EPA would in particular penalize San Francisco, which happens to be Democratic House Speaker Nancy Pelosi’s district.

“We’re going to be giving San Francisco — they’re in total violation — we’re going to be giving them a notice very soon,” Trump said. “We can’t have our cities going to hell.”

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In their letter, the House Democrats pointed to what they described as “conflicting logic” in the EPA’s case.

When he sent his letter, Wheeler said California should withdraw older plans and consult the EPA in drafting new SIPs, which, if rejected by the agency, could cost the state billions of dollars’ worth of highway funding.

He also criticized California for a “backlog” of 130 SIPs from local air regulators that were pending before the EPA.

The Democrats said the agency is failing to process those plans promptly and has overcounted the number of areas in the state that don’t meet air quality requirements under federal law.

According to the EPA, the number of such regions in California is 82. But state officials say that’s far too high.

“As CARB has pointed out, in arriving at this number, EPA at times counted one single area repeatedly and included sovereign tribal communities for which the state is not responsible,” the letter says. “When accounting for these miscalculations, the number of nonattainment areas is actually 20, far fewer than the original estimate of 82.”

Separately, the EPA IG is examining recordkeeping practices of Ryan Jackson, Wheeler’s chief of staff at the agency. Jackson has refused to turn over records related to congressional witness testimony.

Sheehan’s office is investigating how agency officials obtained copies of recent witness statements before they were made public.

“The particularly serious or flagrant problem I am reporting concerns two instances of refusal to fully cooperate and provide information to the IG, one during an audit and one during an administrative investigation,” Sheehan wrote Oct. 29. “They center on a single employee — Chief of Staff Ryan Jackson.”

The EPA said it is cooperating with the IG and defends its responses to that office as appropriate.