FBI investigation of a Virginia man led to what the agency calls its largest-ever seizure by number of finished explosive devices.

The FBI is working to determine the plans of a 36-year-old suspect after investigators discovered over 150 explosives, primarily pipe bombs, on his 20-acre farm. According to the FBI, this is the largest cache of explosives ever found in the bureau’s more than 100-year history.

Prosecutors are fighting to keep a Virginia man behind bars after they say investigators found what could be the largest number of “finished explosive devices” in FBI history at his 20-acre home near Norfolk.