Martin Shkreli, the so-called "Pharma Bro" who became notorious after hiking the price of a life-saving drug by 5,000 percent, is reportedly in solitary confinement after using a contraband mobile phone to continue running his business while in prison.

Shkreli, who turned 36 on March 17, was reportedly sent into solitary confinement last month at the Federal Correctional Institution in Fort Dix, New Jersey, reports Forbes, citing two sources who claimed knowledge of Shkreli's situation. The Bureau of Prisons told Forbes it couldn't comment on Shkreli's whereabouts, saying it can't release information about individuals, although it said Shkreli's mobile phone use was under investigation.

An inmate at the same prison as Shkreli told Forbes that the hedge fund CEO was still in solitary confinement as of Sunday. The inmate, Justin Liverman, told the publication that cellphones are relatively easy to obtain at the Federal Correctional Institution, with inmates renting phone time from others or paying about $1,000 to secure a phone, even though cellphone usage for inmates is prohibited. Liverman is serving five years for computer hacking.

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Shkreli turned to illegal cellphone use to run the drug company Phoenixus AG, formerly known as Turing Pharmaceuticals, while serving a seven-year sentence for lying to investors in two failed hedge funds, The Wall Street Journal reported last month.

“Pharma Bro” Martin Shkreli is in jail for fraud, yet was able to continue his scam thanks to a contraband cellphone. My bill would allow prisons to jam cellphones so inmates can’t continue their crime sprees from behind bars:https://t.co/xZDwrAN3lO — Tom Cotton (@SenTomCotton) April 1, 2019

Using the contraband mobile phone, Shkreli reportedly fired the company's chief executive, who was on a safari. Shkreli was also regularly posting to social media, creating a new Twitter account under the name @sriole, although that account was no longer active soon after the Journal's report. Previously, Shkreli had been suspended from Twitter for violating its rules against harassment.

Reports of Shkreli's mobile phone use while in prison prompted one lawmaker to propose a bill last month that would jam mobile phone signals at prisons, blocking contraband usage.

"'Pharma Bro' Martin Shkreli is in jail for fraud, yet was able to continue his scam thanks to a contraband cellphone," Sen. Tom Cotton, R-Arkansas. "My bill would allow prisons to jam cellphones so inmates can't continue their crime sprees from behind bars."