Abu Qatada was re-arrested earlier this month after being linked to the publication of extremist material on the internet, police have said.
Counter-terrorism officers investigating extremist material found words "attributed" to the 52-year-old and are attempting to determine whether he was involved in their publication.
According to Deputy Assistant Commissioner Stuart Osborne, officers were investigating a range of publications in in a number of languages.
He said: "When we searched his house before his arrest that was a police search in relation to investigating some publications, to see if that was anything that reached a criminal threshold.
"There is an awful lot of media that needs to be looked through."
UK border officials re-arrested Abu Qatada on 8 March for breaching the terms of his bail and he was returned to prison.
He had been under a strict 16-hour curfew after winning an appeal against deportation to Jordan in November where he was to face trial on terror charges.
Despite Theresa May receiving special assurances from Jordan that evidence gained using torture would not be used against him, he was released under bail.
The Home Secretary has appealed against the decision to allow Abu Qatada to stay in the UK three days after the radical preacher was arrested for breaching bail conditions and is awaiting the outcome.
A hearing over whether he should be granted bail was due to be held on Thursday but was delayed.