Nearly 58,000 absentee ballots for the US presidential election may never have reached Florida's Broward County voters, who had requested them more than two weeks ago, election officials said.

State police are investigating the matter, they said.

Hundreds of people have called the county elections office to complain that they never got their ballots. The phone system was so overwhelmed some frustrated voters could not get through.

The election office said the problem involved ballots mailed on October 7-8, though the number of those actually missing was uncertain. Some absentee ballots mailed on those dates have already been returned to be counted.

"We are trying to determine what occurred and whether there was any kind of criminal violation," said Paige Patterson-Hughes, spokeswoman for the Florida Department of Law Enforcement.

The county blamed the US Postal Service. "That is something beyond our control," Deputy Supervisor of Elections, Gisela Salas, said. "We really have no idea what's going on."

But postal officials said the post office has not to blame.

"We have employees that we assign to handle the absentee ballots that come in," said Enola C Rice, a Postal Service spokeswoman in South Florida. "So all the absentee ballots that are received by the Postal Service are processed and delivered immediately."

Absentee voters who did not receive a ballot can request another, which officials said would be sent by overnight mail.