A 23-year-old man allegedly drowned his mother in the pool of their ritzy US$1.9 million ($2.6m) home in New York.

Denis Cullen jnr was arrested on Wednesday after detectives found the body of 63-year-old Elizabeth Cullen in the backyard of their Cold Spring Harbour home in Long Island.

Her lifeless body was found about 4pm local time after police received a request to check on her welfare.

"Lloyd Harbor police received a call about a possible, intentional drowning," Suffolk County Police Commissioner Tim Sini said. "The evidence suggested that she was intentionally drowned, as the call indicated."

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It is unclear who called police.

Sini said Cullen jnr returned to the scene of the crime and cops cuffed him.

He has no previous criminal history and did not resist arrest, police told CBS.

He has been charged with second-degree murder is expected to face a judge today.