Sixteen American citizens in Europe received mail containing white powder . `` We know where the package is coming from , '' the official said , but declined to elaborate . Tests show powder harmless in most cases ; investigation pending in 16th case . U.S. Embassy official in Madrid : ` ` We know where the package is coming from ''
Sixteen American citizens in Europe received mail containing white powder . Tests show powder harmless in most cases ; investigation pending in 16th case . U.S. Embassy official in Madrid : ` ` We know where the package is coming from ''