"I know there are a number of people who would love an excuse to get after Iraq," said a top federal scientist involved in the investigation.

Use new information technology to share information with other federal and academic scientists.

The fliers also pass along information, based on the work of federal criminal behavioral scientists, about who investigators believe may have sent the letters.

The $14-million-a-year program was created in the Reagan administration, and its data are used by many state agencies and federal scientists.

The children's higher levels of residues could be a result of several factors, federal scientists said.

Large-scale production, the federal scientist said, would require much equipment, suggesting state sponsorship.

The death rate from influenza rose markedly in the 1990's, federal scientists reported yesterday.

Since the mid-1970's, federal scientists say, the average global surface temperature has risen at a rate equal to 3.5 degrees per century.

"Basically," said a federal scientist, "this says there's no higher level of sophistication than what someone might do in a garage."

The population there crashed 90 percent, federal scientists say, while in other areas the birds were hit less hard.