Federal authorities are investigating claims that Martin Shkreli has been running his pharmaceutical company from behind bars.

The U.S. Bureau of Prisons said Friday that it has opened an inquiry into whether the so-called "Pharma Bro" used a contraband smartphone inside a federal prison in New Jersey.

The Wall Street Journal reported this week that Shkreli has been calling the shots at Phoenixus AG, a drug company formerly known as Turing Pharmaceuticals, despite the seven-year sentence he is serving for lying to investors in two failed hedge funds.

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The newspaper said he fired the company's chief executive, who was on a safari, a few weeks ago in a call made from jail. It says Shkreli is also regularly posting to social media, creating a new Twitter account under the name @sriole. As of Friday afternoon, that account was no longer active on Twitter. Previously, Shkreli had been suspended from Twitter for violating its rules against harassment.

Very important request: Can anyone please reply with the correct lyrics to the Spanish verse on Meek Mill's "Uptown"? I... Posted by Martin Shkreli on Saturday, January 12, 2019

Shkreli is also reportedly posting to a personal blog, where he writes about famous figures and criticizes the judicial system, according to The Journal. He's also said to be using both his mobile phone and prison computers to read up on pharmaceutical research, part of his plan to return to his pharmaceutical business when he's released in 2023.

Prisoners caught with a phone can face up to an additional year if convicted.

Shkreli's defense attorney, Benjamin Brafman, declined to comment.