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Washington DC: US President Donald Trump said on Saturday that “multiple individuals” had been arrested for vandalising the Lincoln Memorial Reflecting Pool, and that problems with a more than $US14 million ($20 million) renovation project had become so severe that the pool would have to be at least partly drained for “necessary repairs”.

The president’s announcement late Saturday (US time), made on social media, was his starkest acknowledgment of the pool’s rapid deterioration in recent days. The water this week became covered by clouds of blooming algae, which were obscuring a floor that had just been painted a shade that Trump has called “American flag blue”. The paint then began to peel off, making it a tourist destination for unusual reasons.

Among those accused of vandalism was David Carter Hearn, 67, a cyclist and a three-time Olympian as a canoeist who says he stopped at the site on Friday just to have a look, then reached down to touch a strip of peeling blue paint mixed with the algae.

The US Park Police arrested Hearn shortly after, accusing him of destroying government property, a crime that can carry up to a 10-year prison sentence. Hearn denies the charge.

“I was just a curious, concerned citizen,” he said in an interview. “I guess I was there at the wrong place, wrong time.”

The administration has not released the names of others accused of vandalising the pool, a crime that Trump said could lead to “years in jail”. In a later post, he said without evidence that vandals had “poured corrosive and destructive chemicals into the Pool”.

The project, one of many that Trump is undertaking around the capital as the US nears its 250th birthday, has faced intense scrutiny, including from engineers and other experts who said the hastily undertaken project was unlikely to undo the problems that have plagued the pool for decades. A construction company tied to Trump that was awarded a no-bid contract painted the bottom of the pool.

Trump on Saturday said he had met with contractors earlier in the day to discuss the state of the pool.

The Interior Department said agency workers had “killed the algae” that had expanded with heat and humidity. But on Friday afternoon, the water was stained by clumps of algae where National Park Service staff members had scrubbed away bright green blooms along the bottom of the basin. The pool’s new coating was also missing large sections, including a gap roughly the size of a park bench. Underneath appeared to be the original concrete basin.