PHILADELPHIA (AP) – A Philadelphia TV station has found at least three instances in which votes were cast in recent elections under the names of people who were long dead.

WPVI-TV dug through a decade’s worth of Philadelphia’s election and death records.

Republican presidential nominee Donald Trump has warned of fraud at Philadelphia polls. He’s specifically raised concerns about votes made by dead people.

Among the three individuals was a woman who died in 2006 but cast ballots in 2008, 2012, 2014 and the 2016 primary election.

Republican City Commissioner Al Schmidt says human error, like poll workers scanning the wrong name, could be to blame.

Experts say cases of voter fraud involving dead people are isolated. They also say it would be an inefficient way to rig a presidential election.