Federal prosecutors said Monday they are seeking pre-trial detention for an Annapolis, Md.-based Navy nuclear engineer and his wife who are facing espionage charges for selling military secrets to people who they thought were representatives of a foreign country.

Jonathan and Diana Toebbe were arrested Saturday in Jefferson County, W.Va., and federal prosecutors say they should be held pending trial because they face a maximum possible penalty of life in prison and are a “serious risk” to flee or obstruct justice.

A criminal complaint unsealed Sunday in U.S. District Court in West Virginia alleges that Jonathan Toebbe reached out to an unidentified foreign country in December, offering to sell secrets, but it was obtained by the FBI, who began communicating with him.

The complaint says Jonathan Toebbe communicated with undercover agents over secure channels, received secret signals and left memory cards with sensitive information embedded in a peanut butter sandwich and a Band-Aid wrapper at pre-arranged locations. His wife was observed assisting, the FBI says.

Toebbe, 42, a former naval officer, held a top-secret security clearance and had worked on projects related to naval nuclear propulsion of submarines since 2012. He was assigned to the Naval Nuclear Propulsion Program, also known as Naval Reactors.

His wife, 45, has been a humanities teacher at the Key School in Annapolis for 10 years. According to their Facebook pages, both are originally from Southern California, and neighbors said they have two children.

They are scheduled for an initial appearance Tuesday morning, with a detention hearing scheduled later in the week. They do not yet have defense attorneys listed in court records.

“The complaint charges a plot to transmit information relating to the design of our nuclear submarines to a foreign nation,” U.S. Attorney General Merrick B. Garland said in a statement. “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.”

Neighbors said federal agents swarmed the Toebbe’s home in the Hillsmere Estates neighborhood of Annapolis, which they purchased in 2014 for $430,000, according to state real estate records. Agents knocked on every door in the quiet, kid-friendly, tree-lined neighborhood wanting to know about the couple’s “patterns of life,” how they acted or whether they ever heard any arguing, the neighbors said.

The information Jonathan Toebbe allegedly provided during the sting included information about Virginia-class nuclear submarine reactors, according to a court document, which he allegedly agreed to provide data from in exchange for thousands of dollars’ worth of cryptocurrency.

With his wife, Toebbe drove June 26 to a location in West Virginia to drop off an SD card, wedged in a peanut butter sandwich, containing restricted material that cannot be shared under the federal Atomic Energy Act, the complaint said. Diana Toebbe appeared to be “acting as a lookout” as her husband left the material, according to the court filing.

During the months of negotiations, the complaint alleges, Toebbe expressed multiple concerns about secrecy and safety. The complaint quoted him as writing this spring: “Is there some physical signal you can make that proves your identity to me? I could plan to visit Washington, D.C., over Memorial Day weekend. I would be just another tourist in the crowd. Perhaps you could fly a signal flag on your roof?”

The undercover FBI contact responded that “We will set a signal from our main building observable from the street.” The FBI then placed a signal “at a location associated with COUNTRY1″ over Memorial Day weekend, it said. Within days, the complaint said, Toebbe confirmed he’d received the signal and was ready to go ahead with a dead drop.

In July, Toebbe and his wife drove to a location in south-central Pennsylvania and allegedly dropped off another SD card with hundreds of pages of schematics, drawings and other documents. The complaint described it as sealed in a Band-Aid wrapper on this occasion.

“This information was slowly and carefully collected over several years in the normal course of my job to avoid attracting attention and smuggled past security checkpoints a few pages at a time,” the FBI quoted Toebbe as messaging them. “I no longer have access to classified data so unfortunately cannot help you obtain other files.”

In late August, Jonathan Toebbe allegedly dropped off another SD card in Virginia, concealed in a chewing gum wrapper.

“There is only one other person I know is aware of our special relationship, and I trust that person absolutely,” the FBI said he wrote in an attached message. The court document said authorities believe that person was his wife.

When he and his wife arrived Saturday in Jefferson County, allegedly for another drop-off, they were arrested.

The complaint said Jonathan Toebbe told the person he was in contact with regarding leaking the data to that he had “considered the possible need” to leave the U.S. on short notice.

“Should that ever become necessary, I will be forever grateful for your help extracting me and my family. I surmise the first step would be unannounced travel to a safe third country with plans to meet your colleagues. We have passports and cash set aside for this purpose,” the document quoted him as writing.

The Navy on late Sunday afternoon provided a summary of Toebbe’s military career that said he joined the service in 2012 in Denver, studied at the Officer Training Command in Newport, R.I., and was a nuclear engineering officer based in Northern Virginia and Pittsburgh. He became a lieutenant in 2016 and left active duty in 2017. He was a human resources officer in the reserves until he left the Navy in December 2020.

The Key School said in a statement that In its statement that it was “in no way connected to the investigation nor any personal criminal activity involving the Toebbes. Diana Toebbe has been suspended from Key School indefinitely pending the outcome of the investigation.”

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(Baltimore Sun reporters Christine Condon and McKenna Oxenden contributed to this article.)