Preliminary tests on the letters indicated the presence of ricin, officials said.
In the letters, the sender threatened Bloomberg with references to the debate on gun laws. Officials say civilian personnel in New York and Washington who came in contact with the opened letters remain asymptomatic.
However, members of the NYPD Emergency Service Unit who came in contact with the letter that was opened at the city’s mail facility on Gold Street in Manhattan on Friday experienced minor symptoms of ricin exposure. The symptoms have since abated, NYPD officials said.