GAINESVILLE, Ga. (AP) — Two Georgia men pleaded guilty to conspiring to get an unregistered explosive and an illegal gun silencer in what prosecutors describe as a plot to attack government targets.

The suspected ringleader of the group, 73-year-old Frederick Thomas, and 67-year-old Dan Roberts entered their guilty pleas during a Tuesday hearing in federal court in Gainesville.

They could face up to five years in prison and a 250,000 fine. They also agreed in the plea deal to cooperate with authorities.

They are among four men arrested in early November after at least seven months of surveillance by an undercover informant who infiltrated their meetings at a Waffle House, homes and car rides. The dozens of hours of recordings the informant made are the linchpin to the government's case against the four.