Chicago, Sep 25 - An American convert to Islam was Thursday charged with a plot to blow up the court building in Springfield, Illinois and trigger mass murder.

Michael Finton, who converted to Islam in jail some time ago to become Talib Islam, was arrested Wednesday after an undercover operation which began in 2007. He has been charged with plotting to blow up the Paul Findley Federal Building in Springfield and murder government employees.

According to documents filed in the court, Finton's plot was unearthed after he was arrested for a parole violation in 2007.

After his arrest, when police searched his vehicle, they found letters mentioning martyrdom and his links with John Walker Lindh, the 'American Taliban' who was captured in Afghanistan by US forces in 2001.

Immediately after this, the Federal Bureau of Investigation (FBI) set up a task force to tail Finton who worked in a restaurant. Court documents say the FBI first used a drug informant to become friendly with Finton who revealed that he wanted to get arms training and fight against Israelis in Gaza.

Then the FBI used another undercover agent to pose as an Al Qaeda operative to 'help' Finton in his plot.