UPDATE 1-Watergate 'Deep Throat' Mark Felt dies at 95

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WASHINGTON, Dec 19 (Reuters) - Mark Felt, the mysterious "Deep Throat" source who helped Washington Post reporters Bob Woodward and Carl Bernstein crack the Watergate scandal that brought down President Richard Nixon, has died at age 95.

Felt suffered from congestive heart failure but the exact cause of his death at home on Thursday was not immediately known, said the Press Democrat newspaper in Santa Rosa, California, 55 miles (90 km) north of San Francisco.

In its report on Felt's death, the New York Times called him "the most famous anonymous source in American history."

Felt, the No. 2 official at the FBI when the Watergate case broke, kept his role in the story a secret for 30 years. Only in 2005, at age 91, was his part made public in an article in Vanity Fair magazine written by Felt's family lawyer.

"I'm the guy they used to call Deep Throat," Felt told attorney John O'Connor.

For years, people had speculated and argued about the identity of "Deep Throat," whose name was derived from the title of a popular pornographic movie.

Vanity Fair scooped Woodward and Bernstein, who had promised not to reveal the name of the star source of their 1974 stories until after his death. But within a day of Felt's unveiling, Woodward wrote of his relationship with Felt.

Woodward said he turned to Felt after he and Bernstein wrote about the break-in at the offices of the Democratic National Committee at the Watergate complex in Washington.