An alleged plot to assassinate Barack Obama "doesn't seem credible," however, it has not been totally ruled out, federal law enforcement officials said Tuesday.

An initial interview by U.S. Secret Service agents found that the "Obama plot" by three suspects arrested in Aurora, Colo., on Sunday could lead to additional charges on top of the guns and drug charges, a spokesman for U.S. Attorney Troy Eid said.

Shawn Adolf and Nathan Johnson are being charged with felony in possession of weapons charges and Tharin Gartrell is being charged with illegal drugs. However he likely will also later be charged with gun charges after he was pulled over and allegedly found with two rifles, high powered scopes, a bullet-proof vest, walkie talkies, two wigs, camouflage clothing and methamphetamine.

They say they also found three IDs in other people's names and what they believe to be methamphetamine.

Eid described the men as "meth heads" who weren't capable of such an attack.

Earlier in the day, a federal law enforcement official in Denver said  it was possible -- but unlikely -- that additional charges could come later.

The law enforcement official in Denver said Tuesday that the group is not expected to be charged with making threatening statements, conspiracy or other national security-related crimes.