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In Maryland, the Department of Transportation is taking precautions following Thursday's mailroom incident at its headquarters in Hanover. The department is not bringing in new mail.
Meanwhile, the U.S. Postal Inspectors are trying to track the origin of incendiary packages sent to Maryland Gov. Martin O'Malley and the state's transportation secretary.
Postal Inspector Frank Schissler of the Washington field division says there were exterior markings on the packages that will help investigators narrow down their origin. But he says the packages didn't have individual tracking numbers because they weren't sent via registered mail or express mail.
The packages produced smoke and small flames when they were opened by state workers Thursday afternoon, but no one was seriously injured. One of the packages -- addressed to O'Malley -- reportedly included a note griping about highway signs that urge motorists to "Report Suspicious Activity."
Schissler says packages are tracked once they enter mail processing plants, and he says the postal service will examine its internal tracking data on the packages.