By David Shortell, CNN

(CNN) -- The father of a former CIA officer killed in Afghanistan in 2001 has formally petitioned for an investigation of extremist comments allegedly made in prison by American Taliban fighter John Walker Lindh, who is scheduled to be released later this week.

In a letter to a Virginia federal court, Johnny Spann said Lindh reportedly "ignored" conditions placed on him in a plea agreement he reached in 2002.

Mike Spann was killed in an uprising of Taliban prisoners in 2001 at a detention facility in Afghanistan where Lindh was being held. After charges that touched off a debate in the early days of the war on terror, Lindh, who was dubbed the "American Taliban," pleaded guilty in 2002 to aiding the Taliban.

He is due to be released from prison this week after serving 17 years of a 20-year sentence.

Spann has protested the early release of Lindh and taken the issue up with lawmakers, including Sen. Richard Shelby, an Alabama Republican, who said last month that he raised the issue with President Donald Trump, who agreed that Lindh should serve his full sentence.

According to a National Counterterrorism Center document reported by Foreign Policy magazine in 2017, Lindh "continued to advocate for global jihad and to write and translate violent extremist texts" from behind bars.

Lindh allegedly "told a television news producer that he would continue to spread violent extremist Islam upon his release," according to the NCTC document, which Spann cites.

Another document reported on by Foreign Policy, from the Bureau of Prisons, said Lindh "made pro ISIS statements to various reporters and was subsequently dropped by counsel" during detention.

In the petition filed Monday, Spann asked the court to order "a thorough investigation of the actions of John Walker Lindh that have been reported by the National Counterterrorism Center."

"Nothing will be gained by not enforcing the Laws of the United States and holding those that break it accountable for their actions," Spann wrote.

CNN has reached out to Lindh's attorneys for comment.

In an interview with CNN Sunday, Spann called for an "intense investigation" into Lindh's alleged prison comments.

"If you were here talking to me today and John Walker Lindh had been in prison for the 17 years of a 20-year sentence and he had been a model prisoner... I would have said he served his time, he's done what they said do. But with all these reports that are out, all these things that have been said and reported, what I am asking to happen is that they do an intense investigation, a thorough investigation of those reports to see if he actually has done that," Spann said.