SALT LAKE CITY (AP) — A government watchdog will investigate whether the U.S. Interior Department broke the law by making plans to open lands cut from a Utah national monument by President Donald Trump to leasing for oil, gas and coal development, a pair of Democratic congress members said Monday.

The Government Accountability Office’s investigation into whether the Interior violated the appropriations law by using funds to assess potential resource extraction in the lands cut from the Grand Staircase-Escalante National Monument is the latest chapter in a long-running saga over the sprawling monument created in 1996 on lands home to scenic cliffs, canyons, dinosaur fossils and coal reserves.

Trump slashed the monument by nearly half in 2017 following a contentious review by former Interior Secretary Ryan Zinke of monuments around the country. Trump ordered the review based on arguments by him and others that a law signed by President Theodore Roosevelt allowing presidents to declare monuments had been improperly used to protect wide expanses of lands instead of places with particular historical or archaeological value.

The GAO investigation comes after U.S. Sen. Tom Udall of New Mexico and U.S. Rep. Betty McCollum of Minnesota, both Democrats, requested the investigation in May. They argue that a section of the appropriations law on the books since 2002 states that no taxpayer money can be used to do pre-leasing studies on lands in monuments that were created by Jan. 20, 2001.

Last year, the Interior made public proposals for managing Grand Staircase, saying its preference for one of the sites would be the “least restrictive to energy and mining development.” That plan also would allow commercial timber harvesting to keep forests healthy.

The public comment period closed on the proposals and the Bureau of Land Management’s website says it intends to finalize the plans later this year.

Interior Department Press Secretary Molly Block said in a statement the agency will provide “factual information” to the GAO and is “confident” the probe will determine the Interior “acted appropriately and within the law.”

GAO spokesman Charles Young confirmed the inquiry. He said it’s too early to known how long the probe into the legal question will take.

Trump in 2017 also downsized the Bears Ears National Monument in Utah, but that won’t be part of the GAO’s inquiry because it was created in 2016 by President Barack Obama.

Environmental, tribal, paleontological and outdoor recreation organizations have separate lawsuits pending to restore the full sizes of the monuments, arguing presidents don’t have the legal authority to undo or change monuments created by predecessors.

Udall and McCollum announced the GAO investigation in a joint news release. Udall is the ranking member of the Senate’s Appropriations Subcommittees on the Interior, Environment and Related Agencies. McCollum is chair of the same committee in the House.

Udall called on the Interior to halt work on proposed management plans until the GAO makes its determination on the legal question.

“National monuments like Grand Staircase-Escalante protect some of our most spectacular wilderness areas and breathtaking lands, and it is imperative that the Department manage them in accordance with the laws passed by Congress,” Udall said in the news release.