A senior National Park Service (NPS) official has said a liner along the bottom of the Lincoln Memorial reflecting pool was “cut with a sharp knife or razor” earlier this month, repeating Donald Trump’s claims of vandalism.

Frank Lands, the deputy director for operations for NPS, made the allegation in a court filing on Wednesday, as part of a lawsuit brought by a nonprofit group seeking to stop the US president’s renovation of the site.

In the document, Lands said that on 9 June, after the renovation project of Washington’s reflecting pool was “substantially complete”, US Park Service police responded to an “NPS report of damage to the reflecting pool”.

The filing states that the damage includes “a caulk over the foam sealant that was cut with a sharp knife or razor and destruction of delaminating surface material”, with Lands adding that “approximately 70 fence post tops” were also “thrown” into the water.

NPS “plans to begin draining the reflecting pool following the Independence Day celebration to conduct repairs, including assessing and repairing any damage to the lining”, Lands said.

The statement comes amid controversy surrounding Trump’s $14.2m renovation project of the reflecting pool, which he pitched as a bid to turn it “American flag blue” ahead of the country’s 250th birthday celebrations.

Only days after the project was completed, an algae bloom turned the water green, and NPS workers were deployed to the site, where they were seen using skimmers and adding hydrogen peroxide to the water in an effort to improve the water quality. Large flakes of the blue coating were later seen peeling from the basin and floating on the surface.

Over the weekend, Trump blamed unidentified vandals for the problems. And on Sunday, without providing further details, he claimed “multiple individuals” had been arrested by US park police for “vandalizing our Nations magnificent Reflecting Poll”.

A three-time US Olympian and canoeist, David Hearn, was arrested on Friday. Hearn, who denies the vandalism claims, told the Washington Post, that after noticing a partly detached piece of the blue liner, he reached into the water to see what it felt like. Moments later, he said he was arrested on misdemeanor charge of destruction of government property.

Since then, Trump and Department of the Interior have faced growing pressure to release photographic and video evidence supporting their claims of sabotage and vandalism at the pool. The administration has yet to release any photos or videos substantiating Trump’s allegations of a 350ft “gash” through the site.

On Tuesday, the New York Times reported that government documents it obtained showed that, while NPS workers had discovered two cuts in sections of foam located between the pool’s expansion joints, the cuts were not directly related to the blue coating that is now peeling, or to the algae bloom. The cause of the cuts was unclear, according to the report.

Meanwhile, on Wednesday, the US park police announced that they were “seeking assistance in identifying the individual depicted here in connection with a Destruction of Government Property investigation.”

They said that the alleged incident occurred on 19 June at the reflecting pool. A video released alongside the statement, shows a person reaching into the pool and appearing to pull something out.