JERUSALEM (CNN) -- A break-in at a prominent polling firm in the United States is causing a stir in Israel, where the Greenberg-Quinlan Research Company was advising the opposition Labor Party's candidate for prime minister.

"Confidential records, materials, various other items, including petty cash, were stolen during the robbery," said District of Columbia Police Sgt. Joe Gentile.

Gentile said that the FBI was investigating the possibility that "certain records were taken," but did not identify what records were removed from the Washington offices of Stanley Greenberg. Greenberg was an advisor to U.S. President Bill Clinton during his 1992 campaign.

But Tal Silberstein, a campaign official for Labor Party leader Ehud Barak, said someone in Greenberg's office had told him the Israeli campaign was the "main focus" of the robbery.

The thieves "knew exactly what they wanted because the only file taken was the one dealing with the Israeli campaign," Silberstein said.

Barak spokeswoman Aliza Goren told Israeli Army Radio that there was as yet no indication of who was involved in the break-in.

"I hope very much this isn't related to our election campaign," she said. "I don't even want to think that this is possible."

Some Labor Party legislators, however, blamed Prime Minister Benjamin Netanyahu's Likud Party. Netanyahu had no reaction to the news, but Likud issued a statement saying it hoped any suspects were apprehended.

Israeli newspapers likened the incident to the Watergate break-in at the Democratic Party Headquarters, which led to the resignation of President Richard Nixon in 1974.

Greenberg and Democratic consultant James Carville were recently hired to advise Barak in his campaign to unseat Netanyahu.

The break-in occurred overnight Monday, Gentile said. Thieves entered the building, just a few blocks from the U.S. capitol, through a vent on the roof.

Reuters contributed to this report.