Three top senators on Friday requested rare multi-agency inspector-general investigations into the Trump administration’s failure to fully implement congressionally mandated sanctions against Russia.

In a letter addressed to the inspectors general of the State Department, Treasury Department and Intelligence Community, the Democratic lawmakers said the administration has not complied with the Countering America’s Adversaries Through Sanctions Act (CAATSA), which was passed overwhelmingly and signed into law last year in part to punish Russia for its election-meddling and its incursions into eastern Europe.

“Several mandatory provisions of the law have not been implemented by the administration, despite strong evidence that actions taken by or on behalf of the Russian government are in violation of the CAATSA sanctions law and applicable executive orders codified by CAATSA,” wrote Sens. Bob Menendez (D-N.J.), Mark Warner (D-VA), and Sherrod Brown (D-OH).

The letter, which was obtained by The Daily Beast in advance of its delivery to the inspectors general, underscores the intensifying campaign that Democrats and some Republicans are undertaking to push back against the Trump administration’s policies toward Moscow and, in turn, urge the White House to be more aggressive. It also marks the latest of many claims from lawmakers that the Trump administration isn’t fully implementing the sanctions regime—and, in some cases, was keeping Congress in the dark as it missed critical deadlines mandated under the legislation.

The House passed CAATSA last summer 419 to 3, and the Senate approved it by a margin of 98 to 2. President Donald Trump signed it into law despite his strong objections to provisions which he argued handicapped his authority. The Daily Beast first revealed the administration’s efforts to weaken the legislation as it was being written, so as to allow for less congressional oversight. But lawmakers on both sides of the aisle were successful in pushing back against an administration that they feared would be too deferential toward Russia.

The legislation was written primarily to target Russia’s defense and intelligence sectors and the countries and entities that do business with them. As written, the law allows for entities that have existing financial relationships with those Russian companies—which were belatedly designated for sanctions enforcement by the State Department last year—to show that they are winding down their financial relationships with those firms and, thus, avoid U.S. sanctions.

Menendez, Warner and Brown said the administration hasn’t put in the work to allow that process to unravel, which is undermining the “mandate and intent” of CAATSA.

“We also remain concerned that the administration has not formally determined whether individuals are conducting significant transactions with the Russian defense and intelligence sectors under Section 231,” they wrote. “Without such determinations, it is impossible to ascertain whether individuals are substantially reducing significant transactions with these entities as outlined in the law.”

The lawmakers also mentioned the Trump administration’s decision to not follow through with additional sanctions last month against Russia over its support for Syrian dictator Bashar al-Assad—just hours after Nikki Haley, the U.S. ambassador to the United Nations, announced on national television that those sanctions would be rolled out.

Haley’s remarks came after the U.S. and its allies blamed the Assad regime for a horrific chemical-weapons attack in Syria. Haley said the sanctions would have targeted Russian entities that provided material support to the Assad regime. But the sanctions were nixed within hours, reportedly at the behest of Trump.

It is rare for lawmakers to request a multi-agency watchdog review for the same general matter. Menendez, Warner and Brown are the top Democrats on the foreign relations, intelligence, and banking committees, respectively, and each has jurisdiction over the agencies responsible for issuing and implementing the sanctions.

The inclusion of the Treasury Department’s inspector general in the letter is notable because the Office of Foreign Assets Control (OFAC), which is a sub-agency within the department, is responsible for enforcing U.S. sanctions against a several countries including Russia, Iran, North Korea and Venezuela. Current and former U.S. officials told The Daily Beast that OFAC is under-staffed and starving for resources at a critical time for the Trump administration’s foreign-policy objectives.

The Trump administration has at times received high marks from congressional Democrats and Republicans for its posture toward Russia—including its imposition of sanctions targeting individuals and entities alleged to have been involved in election interference, its decision to provide lethal defensive weapons to Ukraine, and its designation of Russian human-rights abusers under the Magnitsky Act.

But they have also called attention to the president’s refusal to outwardly criticize Russian President Vladimir Putin, his attacks on the investigations into Russian interference in the 2016 presidential election, and what lawmakers view as an absent whole-of-government approach to counter the Kremlin.