A Navy engineer accused of hiding restricted information about nuclear-powered submarines in a peanut butter sandwich faces espionage-related charges, according to federal court documents unsealed Sunday.

The man, Jonathan Toebbe, 42, was arrested Saturday in West Virginia on suspicion of conspiracy to communicate restricted data and other crimes, federal prosecutors in the state's northern district said in a statement.

His wife, Diana Toebbe, 45, a teacher in Maryland, was arrested on allegations that she assisted him.

A criminal complaint alleges that Toebbe — who began working with the Navy in 2012 — sent a package containing military documents and other files to a military intelligence agency in the country he was trying to establish a relationship with.

The package wound up with an FBI attaché in the country, which is not identified, the complaint says.

Beginning in February, an undercover FBI agent began emailing Toebbe — who is alleged to have used the moniker "Alice" — through an encrypted messaging service, according to the complaint, which says that in the following months, he provided the agent with documents containing restricted details about Virginia-class submarines, which are nuclear-powered fast attack warships.