WASHINGTON (CNN) -- The FBI has taped conversations between Republican Sen. Ted Stevens of Alaska and an oil company executive who has pleaded guilty to bribery, according to a source with knowledge of the investigation.

Sen. Ted Stevens, who has represented Alaska since 1968, walks past a photographer on Capitol Hill in July.

The calls were between Stevens, who is up for re-election in 2008, and Bill Allen, then CEO of oilfield services firm VECO Corp., the source said Thursday.

In May, Allen and another VECO executive pleaded guilty to paying more than $400,000 in bribes to Alaska public officials.

The source would provide no further details, and the FBI declined comment on the matter Thursday night.

The existence of the tapes was first reported by The Associated Press.

Federal agents searched Stevens' home outside Anchorage in July in connection with a wide-ranging Alaska corruption probe, which also has snared a state lobbyist and led to bribery and conspiracy charges against three current and former state legislators.

Stevens' office had no comment beyond a statement previously issued to reporters in which the GOP's longest-serving senator urged constituents "not to form conclusions based upon incomplete and sometimes incorrect reports in the media."

Stevens, 83, was chairman of the Senate Appropriations Committee until Democrats won control of Congress last year. He has represented Alaska in Washington since 1968 and is renowned for his prowess in steering federal funds to his vast, sparsely populated state.

In May, the Anchorage Daily News reported that federal agents were asking contractors who carried out an extensive renovation of Stevens' home to turn over their records from the job. One contractor told the newspaper that he was asked to appear before a grand jury in December.

FBI agents also raided the office of Stevens' son, then-state Senate President Ben Stevens, in September 2006. The younger Stevens has not been charged in connection with the probe. E-mail to a friend

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