Bourhan Hraichie, 19, was charged on Wednesday over some documents allegedly found in his cell, one of which allegedly related to a threat to kill someone.

Fairfax Media understands the documents included a handwritten letter that Mr Hraichie intended to send outside jail containing plans to behead people.

It is understood in it he threatened to kill Mr Severin, the corrective services commissioner.

Mr Hraichie was moved to SuperMax prison recently after he allegedly tried to carve an Islamic State-related slogan into the head of his cellmate in Kempsey jail.

He allegedly choked his cell mate, Michael O'Keefe, poured boiling water on his face and then carved "e4" into his forehead, short for the terrorist group's "eye for an eye, tooth for a tooth" mantra.

Mr Hraichie was moved to SuperMax and charged with causing grievous bodily harm and choking after the incident in April.

On Wednesday, he was charged with a further three offences including delivering a document threatening to kill a person.

Police seized the material from his cell at Goulburn jail following an investigation that involved Corrective Services officers.

The teenager has also been charged with making a document connected with the preparation for a terrorist act and doing an act in preparation for or planning a terrorist act.

He will face Central Local Court on October 12 in relation to the fresh charges.

"There is no current threat to the community as a result of today's activity," police said in a statement.