Security officials at the U.S. Capitol became well prepared for chemical and biological attacks through the mail after the 2001 anthrax scare.

So when a deadly poison called ricin was sent in letters to Senate Majority Leader Bill Frist's office, the federal government was ready. Biohazard protocols for the entire Capitol complex included escape hoods for employees, biohazard-blocking filters in air conditioning ducts and mail screening and irradiation for all incoming mail.

“This body is — I hate to say it this way — but it's so much the better for what happened [after the anthrax attacks],” Senate Sergeant-at-Arms William Pickle, a former Secret Service agent who is in charge of providing security for the Senate, told The Associated Press. “I think the protocols and the processes that we have implemented here have made our chances of succeeding and doing things the right way so much better.”

The Capitol was ill-prepared in 2001 for the anthrax attack, with the spores entering the air of the Hart Senate Office Building and circulating before officials could warn people or get the building evacuated. Hundreds of panicked Senate staffers and employees were forced to take Cipro and other antibiotics to combat possible infection days after the letter was opened.

While the safety protocols didn't stop the ricin from reaching Senate Majority Leader Bill Frist's offices on Feb. 2, security officials were able to quickly determine that it hadn't become airborne. The Senate workers who had come in contact with the ricin were sent home later that night after being decontaminated.

Many Capitol mail rooms were sealed off, and people who may have been exposed were decontaminated by having them shower and bag the clothes they were wearing. They also closed Senate office buildings and prepared to collect all of Congress' mail for further testing.

“We have come a long way,” Democratic Sen. Tom Daschle, a victim of the 2001 anthrax mailings, said. “The fact that we have filters in all of the ventilation systems throughout the buildings gives us an opportunity to check almost instantaneously for the degree to which any toxic material may have spread.”

Investigators are now trying to determine how the ricin wound up on a mail-opening machine in Frist's office. The machine and all the letters from the Tennessee Senator's mailroom in Washington were taken to the Naval Medical Research Center in suburban Maryland for further testing.

There may be a connection to another letter containing a small vial of ricin and addressed to the White House, which was intercepted Nov. 6 by the Secret Service and bore a postmark from Chattanooga, Tenn.

That letter was nearly identical to one found at a mail-sorting facility in Greenville, S.C., on Oct. 15. The letters, signed “Fallen Angel,” complain about new rules requiring more rest for truckers and threaten use of more ricin if they are not repealed.

Meanwhile, some lawmakers are now questioning whether it will ever be safe again to open and read unsolicited letters from their constituents. Despite the flood of e-mails, faxes and telephone calls that Congress receives daily, handwritten and typed letters are still the main way members of the House and Senate correspond with the people who elected them.

“Most people still send letters, about 5,000 a week in my office here in Washington, so it's still the principal method by which people will communicate with us,” said Sen. Mike DeWine (R-Ohio).

It was the second time since October 2001 that congressional interns opening letters have discovered a deadly poison. “We can't continue to put these young interns in danger like this,” said Sen. Trent Lott, R-Miss., chairman of the Senate Rules Committee.