Three Plants Affected The last contamination incident, on Sept. 29, infuriated safety officers in Washington, who ordered the building closed.

A similar contamination incident occurs in Chingola in 2006.

Yizheng environment is still in a fine shape although there have been complains from residents for air pollutions and contamination incidents happened.

Yet even as contamination incidents increase, Dr. Crawford and other officials acknowledge that the Federal Government's record of detecting threats has been spotty this year.

He said stringent safety procedures had kept that company from having any contamination incidents.

Following a major contamination incident, all potential pathways of internal exposure should be considered.

The contamination incident followed three separate inspections of the plant since 1986 by investigators from Energy Department headquarters, who had severely criticized Rocky Flats's managers and safety programs.

Guidance documents and planning tools to improve the quality and efficiency of measures taken to respond to accidental or purposeful contamination incidents are described below.

Mr. Giuliani said he would have preferred being informed more quickly about the contamination incidents, noting that the city could then have notified the public sooner.

This position is favored by many environmental and consumer groups and by food companies, which fear that a contamination incident would hurt sales and undermine public confidence in food safety.