WASHINGTON - US authorities are investigating a potential ricin attack at Joint Base Anacostia-Bolling in Washington DC, Senate Majority Leader Harry Reid said Tuesday.

Reid was quoted by Washington Post as saying the incident involved the "same substance" as recent letters sent to President Barack Obama and Senator Roger Wicker. He provided no details.

Other reports indicated the package was found at a Defense Intelligence Agency headquarters mail-sorting facility at the base.

Earlier in the day, the man accused of sending ricin-laced letters to Obama and Wicker was released, after officials canceled a detention and preliminary hearing.