Duo thought they were leaving nuclear secrets in sandwiches, gum wrappers for other governments — until the FBI swooped in.

A U.S. engineer and his wife are accused of trying to sell nuclear-submarine secrets to another country, according to federal prosecutors.

Jonathan and Diana Toebbe were arrested in West Virginia on Oct. 9. Prosecutors say for nearly a year, the two sold classified information about nuclear-designed ships to a person who they thought was a rep from another country. In reality, the person was an undercover FBI agent.

Jonathan Toebbe worked for the Department of the Navy as an engineer at the Naval Nuclear Propulsion Program, according to prosecutors. He had national security clearance, which gave him access to the information.

The information included design elements, operating parameters and performance characters.

On April 1, 2020, Jonathan Toebee sent a package to a foreign government and listed a return address in Pittsburgh, according to prosecutors.

The package included classified info and instructions for how to obtain more, according to prosecutors. Federal officials have not released which country the Toebbes thought they were working with. Jonathan Toebbe then started to email with the individual from the country but was the FBI.

The two talked for several months until Jonathan Toebee agreed to sell data for thousands of dollars in cryptocurrency.

In June 2021, the undercover agent sent $10,000 in cryptocurrency as a “good faith” payment.

Weeks later, Jonathan and Diana Toebbe went to West Virginia and placed a SD card within a peanut butter sandwich at a dead-drop location, according to prosecutors.

The agent got the card then sent another $20,000 to the couple, according to prosecutors. Jonathan Toebbe sent the decryption key for the card. The information on the card was data for submarine nuclear reactors.

In August, Jonathan Toebbe did another drop in eastern Virginia, this time in a chewing gum package. That information was similar and the Toebbes received $70,000.

On Oct. 9, the couple was arrested when Jonathan Toebbe did another drop at another location in West Virginia.

The duo has been accused of violating the Atomic Energy Act.