Additional tests were being run on the letters Tuesday as officials zeroed in on possible suspects near Amarillo, Texas, where the letters were postmarked.
"Most of these letters contain a powder substance with a threatening communication," the FBI said in a statement.
"Even sending a hoax letter is a serious crime," the FBI said.
A law enforcement official said the letters were mailed to Chase bank branches in or near Atlanta, Chicago, Columbus, Ohio, Dallas, Denver, Newark, N.J., New York City, Oklahoma City and Washington. They all appear to be from the same source and began showing up at the banks on Monday, according to the official who spoke on condition of anonymity because he was not authorized to discuss the matter publicly.
A second law enforcement official, also speaking anonymously under the same conditions, said authorities were looking into whether the letters were sent in anger due to the cratering economy. Authorities would not release the text of the letters, but Gary Johnson, a spokesman at the FBI field office in Oklahoma City, said the threat was "based on past actions of the bank" and that the letters implied that the opener was going to die.
U.S. Postal inspector JoJan Henderson confirmed that the letters appeared to be related. The U.S. Postal Service and state and local officials also were investigating.
The letters were sent against a backdrop of eroding trust in U.S. financial institutions. The country is battling its worst financial crisis since the Great Depression of the 1930s, where borrowing money has become much more difficult and a lot more expensive for consumers and businesses. The situation has roiled Wall Street and threatens to plunge the U.S. economy into a deep recession.
One of the main goals of Washington policymakers is to restore confidence in the banking and financial system. To do so, the government has announced a flurry of drastic actions in recent weeks. The government is injecting billions into the country's biggest banks in return for partial ownership. It is also guaranteeing new bank debt and has boosted deposit insurance from $100,000 to $250,000.
The crisis has left home foreclosures at record highs, has shriveled Americans' nest eggs and has catapulted unemployment.
No injuries were reported after any of the letters were opened. Mary Jane Rogers, a spokeswoman for JPMorgan Chase & Co., said some employees, including a pregnant woman, were examined as a precaution.
Eight banks in the Denver area and eight in the Oklahoma City area received letters containing white powder, officials there said. All Denver branches reopened Tuesday.
Nine branches in New Jersey and a Chase credit card center in Elgin, Ill., also received similar threatening letters, said Greg Hassell, a JPMorgan Chase spokesman in Houston. The credit card processing center in Elgin is about 30 miles northwest of Chicago.
Susan Olafson, public information officer for the city of Elgin, said the facility there received two letters, one Monday night and one Tuesday. She said both letters were mailed from Amarillo.
Hassell said authorities were in the process of clearing those locations, and some of those nine New Jersey branches were still closed as of Tuesday afternoon.
One of the letters was received at a Federal Deposit Insurance Corp. building in Dallas and another at a U.S. Office of Thrift Supervision branch in nearby Irving. The letters were similar to those received in other cities and no one was hurt, FBI spokesman Mark White said in Dallas.
Jeff Lyttle, a spokesman for JPMorgan Chase in Ohio, said a Chase branch in the Columbus suburb of Grove City received a threatening letter on Monday. The branch was closed for a short time and reopened at about 2 p.m., Lyttle said. No employees were injured. Lyttle said he was unaware of other Chase branches in Ohio that received letters.
All the suspicious mail that has been tested has turned out to be harmless, Hassell said, but other Chase branches around the country "are on alert."
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