An employee of the Russian Consulate in New York was found dead there early on November 8 with a head wound, though police were still trying to determine his exact cause of death.
The man, who was in charge of security at the installation, was found unconscious before 7 a.m. local time inside the consulate in the Upper East Side neighborhood near Central Park, a New York Police Department spokesman said.
He has not yet been identified, though his age was given as 63.
Nikolai Lakhonin, a spokesman for the Russian Embassy in Washington, said preliminary indications are the man died of a heart attack.
The New York consulate said on Facebook that no signs of violent death were found.
Police and embassy officials are awaiting the results of the medical examiner's autopsy to determine a cause of death.
A former aide to Russian President Vladimir Putin was found dead in a Washington hotel last year, prompting wild theories over the murky circumstances of his death.
But prosecutors said last month his sudden death was an accident that occurred after days of heavy drinking and successive falls.