SAN FRANCISCO—Carl Mark Force, the head of a Baltimore-based team of law enforcement that investigated the Silk Road drug trafficking website, has pled guilty to extortion, money laundering, and obstruction of justice.

Standing before US District Judge Richard Seeborg in an orange inmate's jumpsuit, Force admitted that he stole from the Silk Road—and its founder Ross Ulbricht—even as he was investigating the website.

Prosecutors described the details of the charges against him in court. Later, as Seeborg questioned Force about each accusation, Force admitted to each one.

Acting as "Nob," the government-sanctioned account through which he interacted with Ulbricht's online persona Dread Pirate Roberts, Force took payments from Ulbricht that he didn't tell his superiors about and diverted the bitcoins into his personal accounts. Ulbricht was tried earlier this year and sentenced to life in prison in May.

He also created a second unauthorized account, "French Maid," from which he collected approximately $100,000 (£64,000) in bitcoins by offering "counter-intelligence" on law enforcement.

An attempt to extort money from DPR using a third account, "Death From Above," wasn't successful.

The government also charged Force with having multiple conflicts of interest, including a contract from 20th Century Fox to be paid up to $240,000 (£153,000) to tell his story for an upcoming movie. It isn't clear how much of that, if any, Force actually got paid. The contract was signed in 2014, and Force didn't reveal it to his superiors at the DEA.

Force was a key source in Wired's Silk Road cover story published in April 2015, which concludes by describing Force's own arrest.

A second conflict involved a company called CoinMKT, which Force worked for and also was a primary investor in. He used his job at DEA to help them run criminal background checks. At one point, he confiscated $370,000 (£237,000) from a CoinMKT user, saying he was taking it on behalf of the DEA, but only put $37,000 in the government account, keeping the rest. (That's more than the $297,000 previously reported.)

The sentencing will take place in October. The plea deal doesn't include a specific sentence. The maximum sentence for money laundering is 20 years. Force has agreed to pay about $500,000 (£320,000) in restitution, according to his attorney. Around $150,000 of that has already been paid.

"He's accepting responsibility," Force's attorney, Ivan Bates, told reporters after today's hearing.

Secret Service Agent Shaun Bridges, another man on the Baltimore task force, has also agreed to plead guilty to government charges against him.