(CNN) -- Charges were dismissed Tuesday against the man accused of sending ricin-laden letters to President Obama and others.
The attorney for Paul Kevin Curtis told reporters Tuesday that federal authorities are looking at another suspect in connection with the crime.
A U.S. attorney dismissed the charges, saying "new information" has been uncovered.
Curtis, an Elvis impersonator from Corinth, Miss., was charged with sending a threat to the president last week after letters containing the poison triggered security scares around Washington. But a preliminary hearing that had been scheduled to continue on Tuesday was canceled and Curtis was released.
Jeff Woodfin, the chief deputy marshal in Oxford, where the case was being heard, said Curtis was no longer in federal custody but did not know the circumstances surrounding his release.
Curtis was accused of sending letters containing "a suspicious granular substance" to Obama, Sen. Roger Wicker, R-Mississippi; and Sadie Holland, a Justice Court judge in Lee County, Mississippi. The FBI said the substance tested positive for ricin, a toxin derived from castor beans that has no known antidote.
The FBI said no illnesses had been found as a result of exposure to the toxin.
Curtis' attorney, Christi McCoy, told CNN last week that her client "vehemently denies the allegations against him."
--Bill Mears, CNN