Threatening letters sent this week to banks and financial institutions declared "it's payback time" and promised death to its readers, according to the text of the message released Thursday.
More than 50 letters mailed to Chase Bank branches and federal regulatory offices in 11 cities this week, most filled with white powder, tested negative for any dangerous toxins.
But the FBI said the hoax still is a serious crime and is investigating the letters as a possible first, if extreme, public backlash over the financial crisis in the United States.
"Steal tens of thousands of people's money and not expect reprercussions (sic)," says the letter, which is written in all capital letters. "It's payback time. What you just breathed in will kill you within 10 days. Thank (name redacted) and the FDIC for your demise."
The FBI would not identify the person whose name was deleted. The FDIC stands for the Federal Deposit Insurance Corp., an independent government-backed agency that insures most deposits in U.S. banks.
Authorities said the letters appear to be from the same source and were focusing on possible suspects near Amarillo, Texas, where the envelopes were postmarked.
Since Monday the letters have been opened in the offices of Chase Bank branches, the FDIC and the U.S. Office of Thrift Supervision, which regulates all federal and many state thrift institutions. They were sent to offices in or near 11 cities: Atlanta, Georgia; Chicago, Illinois; Columbus, Ohio; Dallas, Texas; Denver, Colorado; Newark, New Jersey; New York City; Oklahoma City, Oklahoma; Phoenix, Arizona; San Francisco, California; and Arlington, Virginia.
An FBI spokesman said letters sent to Oklahoma were filled with harmless calcium.
The U.S. Postal Inspection Service has offered a reward of up to $100,000 for help in arresting the letter mailers.
Authorities "are following several good leads, but we are always looking for more information," said FBI spokesman Rich Kolko. "And we hope that when people see this letter and writing style, it will encourage someone with information to contact the FBI or other authorities."