It happened around 10 a.m. inside the TransUnion offices in the 1500 block of Chester Pike.
A Delaware County Emergency Management official said an employee inside the offices found an unknown white substance in an envelope that had been delivered.
As a precaution, 11 people were decontaminated inside the county's hazmat response trailer showers.
Tests by the FBI and the county's hazmat team subsequently determined the substance, which appeared to be a crushed pill, posed no danger.
Officials said there is no need for any further investigation.