A U.S. Navy nuclear engineer and his wife have been charged with selling secret information about nuclear submarines to an undercover FBI agent who posed as an operative for a foreign country, the Justice Department said on Sunday.

Jonathan Toebbe and his wife, Diana, were arrested on Saturday in West Virginia and charged with violating the Atomic Energy Act, the Justice Department said in a statement. They are scheduled to appear in a West Virginia federal court on Tuesday.

Toebbe, 42, a Navy nuclear engineer with top secret security clearance, sent a package of restricted data to an unidentified country in 2020 and later began selling secrets for tens of thousands of dollars in cryptocurrency to an undercover FBI agent posing as a foreign official, the Justice Department said.

At one point, Toebbe hid a digital memory card containing documents about submarine nuclear reactors in half a peanut butter sandwich at a “dead drop” location in West Virginia, while his wife acted as lookout, the Justice Department said.

The memory card contained “militarily sensitive design elements, operating parameters and performance characteristics of Virginia-class submarine reactors,” according to a federal court affidavit.

Another memory card was concealed in a chewing gum package, the Justice Department said.

Toebbe received separate cryptocurrency payments totalling $100,000, according to the Justice Department.

Officials said Toebbe and his wife, who are from Annapolis, Maryland, were arrested after placing yet another memory card at a drop site in West Virginia. They were charged with conspiracy and “communication of restricted data,” according to a criminal complaint.

No attorney for the Toebbes was listed in either the court documents or the Justice Department statement.

“The complaint charges a plot to transmit information relating to the design of our nuclear submarines to a foreign nation,” said Attorney General Merrick B. Garland. “The work of the FBI, Department of Justice prosecutors, the Naval Criminal Investigative Service and the Department of Energy was critical in thwarting the plot charged in the complaint and taking this first step in bringing the perpetrators to justice.”

The couple and the FBI agent repeated this process two more times, the first on Aug. 28 and again on Oct. 9. Each time the couple would receive a “good faith” payment and then deliver an SD card to a location in West Virginia, with the FBI agent recovering it and paying the couple more money for an access key to decrypt the SD card.

On their third visit to West Virginia, however, the FBI arrested the couple, the DOJ reported.

The Toebbes have been charged in a criminal complaint alleging violations of the Atomic Energy Act. They will have their initial appearances on Oct. 12, in federal court in Martinsburg, West Virginia, per the DOJ.