Terry Nichols, arrested two days after the 19 April explosion, is a close friend of Timothy McVeigh, the army veteran identified by FBI officials as the prime suspect in the bombing. Mr Nichols, 40, served in the army with Mr McVeigh, 27, and is understood to have shared his extreme anti- government views.
USA Today reported yesterday that investigators searching Mr Nichols' Kansas home had found a receipt for a ton of ammonium nitrate, an ingredient allegedly used to concoct the Oklahoma bomb. Mr McVeigh's fingerprint was found on the receipt, the paper said.
In an extraordinary twist to what is probably the US's most expensive and wide-ranging criminal investigation, it emerged yesterday that the most wanted man in America - also sought in connection with the Oklahoma bombing - may be a 12-year-old boy: Josh Nichols, Terry Nichols' son.
The boy, who is chubby-faced and has close-cropped hair, bears a resemblance to the sketch of "John Doe 2", the unknown suspect with a $2m price on his head whom the FBI have been trying to track down for the past three weeks.
Josh Nichols, interviewed by the FBI for more than 10 hours this week, is not believed to have had a role in the bombing but investigators suspect he may have been with Mr McVeigh when he rented the lorry that carried the bomb. The sketch was based on descriptions by rental company employees.
As to the widely publicised report that John Doe 2 had a tattoo on his left upper arm, an FBI source said: "We've heard this was a kid who was into those temporary, stick-on tattoos."