The first letter was opened at a New York City mail center in Lower Manhattan on Friday, the police said. Although staff members at the mail center do not appear to have become ill, several police officers who came into contact with the letter's contents "indicated some mild symptoms the next day, including diarrhea," and they are being treated in hospitals, the New York Police Department's spokesman, Paul J. Browne, said on Wednesday afternoon. "They're being checked out as a precaution."
The second letter, which was opened on Sunday in Washington, was addressed to Mark Glaze, the director of Mayors Against Illegal Guns, a group Mr. Bloomberg helps run and finances, officials said. No injuries were reported as a result of that letter, Mr. Browne said.
A spokesman for the Federal Bureau of Investigation, J. Peter Donald, confirmed that the bureau was investigating the letters, but declined to comment further. Both letters were identical in content, bore references to the debate over gun regulation and contained written threats to Mayor Bloomberg, Mr. Browne said.
Both letters bore the same postmark, Mr. Browne said, indicating they had been sent from roughly the same time and place; he declined to say where they were mailed, but added that "something about the way it was addressed" raised suspicion about the letter sent to New York.
Mr. Browne said that "civilian personnel in New York and Washington who came in contact with the opened letters remain asymptomatic."
The letters contained a "pink, orange oily substance," Mr. Browne said, which tested positive for ricin on Wednesday at the National Bioforensic Analysis Center in Maryland. Earlier tests, performed locally, also indicated ricin, Mr. Browne said.
Mr. Browne said the Police Department, whose Intelligence Division is investigating the case along with the F.B.I., has handled "scores, if not hundreds" of emergency calls involving suspicious powders over the years. But since the anthrax attacks of 2001, Mr. Browne said, "each of those cases have been negative," until this one.
Questioned about the letters on Wednesday night, Mayor Bloomberg said: "There's 12,000 people that are going to get killed this year with guns and 19,000 that are going to commit suicide with guns, and we're not going to walk away from those efforts. And I know I speak for all of the close to 1,000 mayors," in Mayors Against Illegal Guns, he said. "This is a scourge on the country that we just have to make sure that we get under control and eliminate."
In April, a former taekwondo instructor from Tupelo, Miss., was arrested on charges of sending ricin-laced letters to the president, a United States senator and a local judge, which were intercepted in mail sorting facilities serving the White House and the Capitol.
J. David Goodman contributed reporting.
