<p>San Antonio FBI spokesman Rene Salinas, who is with the agency's joint terrorism task force, said it still isn't clear what the substance is. He said FBI testing conducted Sunday in Maryland came back negative for ricin, a deadly and easy to produce poison extracted from castor beans, and it is unlikely further testing will be done.
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"There were no proteins in there to indicate it was in fact ricin," Salinas said. </p>
<p>A field test conducted by state authorities on the substance had come back earlier this week positive for ricin or a substance very close to it, Texas Department of State Health Services spokesman Doug McBride said. </p>
<p>Salinas, however, said the state's field test was "just a quick test and they don't check for the proteins in ricin." </p>
<p>The FBI spokesman said it isn't clear whether the FBI will continue with its investigation into how the mystery substance ended up in the roll of quarters. If it was put there as a joke, Salinas said "it was an extremely bad joke."
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