(Kacper Pempel/Reuters)

The allure of the dark world of online drug markets was too much to ignore for even the federal agents investigating it.

Carl Mark Force, a former Drug Enforcement Administration special agent working with a Baltimore-based team investigating the online drug market Silk Road, admitted to squeezing about $200,000 worth of the digital currency bitcoin from the site's founder during the course of the case.

Force is one of two federal agents the government accused of using the Silk Road investigation for their own gain. Another investigator, former U.S. Secret Service forensics expert Shaun Bridges, reached a plea agreement with prosecutors last month, according to Bloomberg.

Force pleaded guilty to extortion, money laundering and obstruction of justice before U.S. District Judge Richard Seeborg of the Northern District of California in San Francisco. He admitted to using his DEA-sanctioned online persona, "Nob," to get money from Ross Ulbricht, the Silk Road mastermind who was sentenced to life in prison this year. According to the plea, Force sold Ulbricht fake IDs and "inside" law enforcement information as part of the investigation, but then tried to hide Ulbricht's bitcoin payments that were worth roughly $100,000 at the time from the government so he could keep it for himself.

Force also admitted to creating another false identity, "French Maid," without the DEA's knowledge and using that persona in a fraudulent scheme where he claimed to sell information about the government's investigation into Silk Road to Ulbricht in exchange for bitcoin payments then worth around $100,000.

“Seduced by the perceived anonymity of virtual currency and the dark web, Force used invented online personas and encrypted messaging to fraudulently obtain bitcoin worth hundreds of thousands of dollars from the government and investigative targets alike," said Assistant Attorney General Leslie R. Caldwell of the Justice Department’s Criminal Division in a statement.

As part of his plea, Force also admitted to working as the de-facto compliance officer for a bitcoin startup without DEA permission. In that role, he directed the company to freeze roughly $337,000 of an account holder's assets without a legal basis, claiming it on behalf of the government. But he tried to make his official report about the seizure look as if only $37,000 — the part that was in cash — was confiscated, keeping about $300,000 worth of bitcoins for himself, according to the plea.

And Force admitted to issuing a fake subpoena to online payment service Venmo after it froze his personal account, as well as entering into a $240,000 movie deal for a film about the Silk Road with 20th Century Fox without DEA approval. (It's unclear whether Force actually received any payments for the movie deal.)

Force's lawyer did not immediately respond to a request for comment, but told Ars Technica that his client has agreed to pay about $500,000 in restitution — some $150,00o of which has been paid.

Force will be sentenced at a hearing in October.