House Democrats are demanding that the Interior department retain documents related to President Donald Trump’s construction projects around Washington after whistleblowers warned that key paperwork has already been destroyed before Democrats take power, congressional sources tell CNN.

The warnings come as the Trump administration is signaling it will accelerate plans for moving ahead with the projects — a key part of what the president sees as his legacy — to lay as much groundwork as possible before the Democrats take over Congress in January.

On Tuesday, the top Democrat in the House Natural Resources committee, which has oversight of the agency that has helped fast-track many of Trump’s projects, plans to issue letters to the Interior Department as well as other federal agencies and private companies, requesting that they “preserve all records and data responsive to oversight” the congressional panel oversees.

The targets of the letters from Rep. Jared Huffman, shared first with CNN, give an early indication of what could be in the crosshairs for investigation when the California Democrat becomes chairman of the committee in the new Congress.