The F.B.I. gave New York officials the most specific of alerts: uncorroborated reports of threats to the city's landmarks.

According to uncorroborated French reports, the blockaders had made some landings in the vicinity of Port Royal, burning a few isolated houses and taking some prisoners.

"There was, maybe 10 days or close to two weeks ago, an uncorroborated report of undetermined reliability about natural gas," Mr. Ashcroft said at a news conference.

While the Mormons' defiance of federal authority in the past had become traditional, some question whether Buchanan's action was a justifiable or prudent response to uncorroborated reports.

EFCA opponents dispute much of her statistical assertions, claiming that they are derived from uncorroborated reports of biased union organizers.

The Nag anti-tank guided missile was cleared for production in July 2009 and there are uncorroborated reports since that it may be purchased by Tanzania, Botswana and Morocco.

The documents also showed that the Justice Department chose not to prosecute, despite two requests by the Internal Revenue Service, because the I.R.S. was relying on uncorroborated reports to make its case, the senators said.

In south-west Scotland, there are uncorroborated reports that a hutting colony has been bulldozed by the site owner.

For if we are ready to discount an uncorroborated report of an event, we must accept that there may be nothing with which to replace it: that the event simply did not happen.