Despite a complex screening system, there is no way to guarantee contaminated blood will not accidently be used in a blood transfusion, a Red Cross official said Saturday.

"No one that I'm aware of in the blood transfusion part of medicine has been able to say that a blood transfusion is 100 percent safe," said Dr. Kenneth Fawcett, director of the Nashville Red Cross center.Researchers still are "working toward achieving that ideal," Fawcett said.

His remarks came in the wake of Friday's announcement by the Food and Drug Administration that lapses in screening of donated blood led to 26 close calls including 20 in Nashville and six in Washington, D.C. where blood contaminated or potentially contaminated with an AIDS virus or hepatitis-B accidently was shipped out to be made into blood-derived drugs or for transfusion.

The FDA said no blood recipients were endangered by the slip-ups.