WASHINGTON (AP) — A liner along the bottom of the Lincoln Memorial Reflecting Pool was cut with a sharp knife or razor this month, causing damage to the foam sealant installed as part of a $16 million rehabilitation project, a top official at the National Park Service says.

The agency reported the June 9 incident to U.S. Park Police, said Frank Lands, deputy director of operations for the park service. Lands made the statement in a court document filed late Wednesday as part of a lawsuit filed by a nonprofit organization to halt the Trump administration's work on the project.

READ MORE: Was the Reflecting Pool vandalized? Experts cast doubt on Trump's claims

His statement does not say whether the damage is a suspected case of vandalism or identify anyone who might have been involved.

The police report indicates damage to the pool, "including a caulk over the foam sealant that was cut with a sharp knife or razor and destruction of delaminating surface material,'' Lands said. About 70 fence post tops also were thrown into the pool, he said.

The statements were the first time the Republican administration has offered specifics for when and how the Reflecting Pool may have been damaged after work on the project was substantially completed.

President Donald Trump and other officials have repeatedly blamed, without evidence, unidentified vandals for peeling paint as well as a "350-foot gash" in the liner and other problems. Six people have been arrested, Trump said this week, without providing details.

Trump pledged to beautify the century-old Reflecting Pool before the nation's 250th birthday celebrations, draining its water and directing the bottom to be painted a color he called "American flag blue." But since the site was restored, its water has been plagued by an algae bloom and pieces of the new coating have appeared to be peeling off the bottom.

His administration faces a self-imposed deadline to complete the renovation before July Fourth. Trump also has said the federal government would release images to substantiate his claim.

Trump said Wednesday that "sick people" had used razors and box cutters to slice portions of the lining.

WATCH: Plagued by algae and peeling paint, Reflecting Pool set to undergo more repairs

The U.S. Park Police posted surveillance footage Wednesday evening and asked for help "identifying the individual depicted here in connection with a Destruction of Government Property investigation." The grainy, 30-second video appears to show a person kneeling down, reaching into the reflecting pool and removing something from the water. Police said it was taken Friday afternoon.

In his statement to the court, Lands said the parks agency plans to begin draining the Reflecting Pool following Independence Day celebrations to conduct repairs, including assessing and repairing any damage to the lining.

The park service completed more than two months of renovations at the Reflecting Pool in early June. The 2,000-foot-long basin was drained and a tinted. A plastic-like rubber lining was installed to waterproof and protect the concrete pool surface, and the pool was refilled with water, Lands said.

The Cultural Landscape Foundation, an education and advocacy group that sued in May to halt work on the project, asked a federal judge to block further renovations.

"It is also not too late to correct course," the group wrote in a filing Monday. It urged the administration to "engage with experts and the public, and make an informed decision about what is best based on the consultations mandated by the law, instead of once again rushing ahead with half-baked ideas."

WATCH: TIMELAPSE: Lincoln Memorial Reflecting Pool refills with water after Trump paint job

Congressional Democrats have called for formal investigations into the pool renovations, saying no-bid contracts for work on the project were awarded to vendors with previous relationships to Trump.

Ohio-based Green Water Solutions was given a $1.7 million contract to install a water-purification system in the Reflecting Pool, while Virginia-based Atlantic Industrial Coatings was awarded $14.7 million to repaint and waterproof the pool's concrete floor.

Oregon Sen. Jeff Merkley, the top Democrat on the Senate appropriations panel overseeing the Interior Department's budget, said the pool renovation appears to be a waste of taxpayers' dollars.

"After railing about waste, fraud and abuse, Donald Trump spent more than $16 million on a renovation of the Reflecting Pool that's now peeling and chock full of algae," Merkley said Thursday. He said this is a "massive waste" of tax dollars and the public deserves "swift answers — and a refund."

Merkley is one of about 10 Democratic senators and House members investigating the pool project.

"Taxpayers deserve a full explanation of how these failures occurred and who will be held accountable for correcting them,'' said another letter, signed by New Mexico Sen. Martin Heinrich and five other senators.

Heinrich is the top Democrat on the Senate Energy and Natural Resources Committee, which oversees the Interior Department.

Associated Press writer Michael Kunzelman contributed to this report.