SEATTLE (AP) _ Sixty-four mechanics at Alaska Airline's Seattle maintenance hangar told company officials they'd been ``pressured, threatened and intimidated'' to cut corners on repairs, prompting the airline to put a top manager on leave while it investigates.

Federal Aviation Administration and airline officials began interviewing the mechanics after the airline told the agency about the complaints, which came in a letter delivered to the carrier on Thursday.

Alaska Airlines also notified federal prosecutors and the National Transportation Safety Board, which is probing the Jan. 31 crash of Alaska Flight 261 off the California coast in which 88 people died.

NTSB Chairman Jim Hall said in a statement nearly all major components of the MD-80's tail section have been recovered and the agency announced the completion of its field study.

Hall also said investigators had found no grease on a crucial portion of the jackscrew that helped control the movement of Flight 261's horizontal tail stabilizer, long a focus of the crash probe.

A spokesman for the plane's manufacturer said the part normally should be lubricated, but he refused to speculate about what the NTSB finding might mean.

The Seattle Times reported on its Web site Friday that the mechanics' letter was triggered by concerns over a recent repair to the horizontal stabilizer and jackscrew assembly on an Alaska MD-80 jetliner.

The mechanics allege the plane was fixed properly only after heated discussions.

FAA spokesman Mitch Barker said the agency was aware there had been recent ``debate'' at Alaska Airlines over a horizontal stabilizer repair. He said the plane was returned to service in proper condition.

A draft of the letter by 64 mechanics quoted by the Times said workers were ``directed ... to do things specifically contradicting'' federal aviation regulations, and alleged they had been ``pressured, threatened and intimidated ... in the daily performance of our work.''

In a statement, Alaska Airlines said about 12 mechanics had been interviewed and that it would immediately ground any planes found to be potentially unsafe.

Robert Falla, the leader of the airline's Seattle maintenance base, has been placed on administrative leave as the investigation continues.

He was not named by the airline or investigators, but told The Times on Friday that ``no aircraft under my authority has ever gone out unairworthy or unsafe.''

``There is nothing I have to hide, and there is nothing Alaska Airlines has to hide,'' he said.

The airline is already the subject of a criminal investigation over alleged maintenance violations at its Oakland, Calif., maintenance base.

A grand jury in San Francisco is investigating whether supervisors signed for repairs that weren't done or that they weren't authorized to approve.