WASHINGTON: The company that managed Hillary Clinton's private email server said it has "no knowledge of the server being wiped," indicating that tens of thousands of emails Clinton said were deleted could be recovered, the Washington Post reported on Saturday.

Clinton, the front-runner for the Democratic presidential nomination, and her aides have said she deleted her personal emails from her time as secretary of state, but unless the server has been "wiped" experts say those 31,000 emails could be recovered, the Post reported.

A representative of the Clinton campaign could not immediately be reached for comment on the report.

The controversy over her use of an unsecured private server to conduct government business while America's top diplomat has cut into her lead in opinion polls for the Democratic nomination to run in the November 2016 election.

Denver-based company Platte River managed the server.

"Platte River has no knowledge of the server being wiped," company spokesman Andy Boian was quoted as saying by the Washington Post. "All the information we have is that the server wasn't wiped."

Republican Senators Charles Grassley and Ron Johnson, chairmen of the Judiciary and Homeland Security committees, respectively, said they would push for the deleted emails to be reviewed if they can be recovered, the Post said.

On Tuesday, Clinton apologized for using a private server rather than the government system.

Clinton has said she sent no information via email that was classified at the time and received no material marked that way.

The Federal Bureau of Investigation is examining the server to see whether any information, including classified information, was mishandled.

The State Department, under a court order, has been releasing more than 30,000 Clinton work-related emails in monthly batches.