Police in Pennsylvania said on Tuesday that the tombstone of Hillary Clinton's father had been knocked over in a possible case of vandalism, the Scranton Times-Tribune newspaper reported, days after she announced her presidential bid.

A person at the Washburn Street Cemetery reported that the gravestone of Hugh Rodham had been overturned, Scranton Police Chief Carl Graziano told the newspaper.

Graziano said the tombstone may have been vandalised. "I'm not sure how else it would have fallen over," he told the Tribune.

The police department in Scranton could not immediately be reached for comment.

Hillary Clinton, who begins the 2016 presidential race as the Democratic front-runner, revealed her candidacy on Sunday. She ran for president unsuccessfully in 2008, losing her party's nomination to then-U.S. Senator Barack Obama.

Cemetery caretaker Paul McGloin said it was later righted, according to the Tribune.

"I hope this had nothing to do with politics because that's just wrong," McGloin he told the paper.