WASHINGTON — Federal prosecutors asked Monday that a Navy engineer remain locked up as they press forward with charges that he tried to sell submarine secrets to a foreign country.

The detention memo for Jonathan Toebbe was filed ahead of an expected appearance in federal court in West Virginia on Tuesday. The Justice Department submitted an identical motion for Toebbe's wife, Diana, who was also arrested Saturday.

Jonathan Toebbe is accused of passing on design information about sophisticated Virginia-class submarines to someone he thought represented a foreign government but who was actually an undercover FBI agent. The identity of the country was not revealed in court documents.

According to the documents, Toebbe reached out in April 2020 to the foreign country to offer information about the submarines and to provide instructions for how to maintain a furtive dialogue. But the package he sent was obtained eight months later by the FBI, which initiated contact with Toebbe through an undercover agent who agreed to pay tens of thousands of dollars in cryptocurrency in exchange for the government secrets.

Toebbe left memory cards containing sensitive documents in pre-arranged "dead-drop" locations, concealing it in one instance inside a peanut butter sandwich and on occasions inside a chewing gum package and Band-Aid wrapper, the FBI says. Diana Toebbe accompanied him on several occasions, including serving as a lookout during one such dead-drop operation in Jefferson County, West Virginia, court documents say.

It was not immediately clear if either of the Toebbes had an attorney.

In the detention memo, prosecutors checked boxes indicating that they believe the Toebbes represent a risk to flee and to obstruct justice. They also checked boxes showing that the prosecution, under the Atomic Energy Act, involves an "offense for which the maximum sentence is life imprisonment or death."