Terror police began the raid on Abu Qatada's London home at 6.30am on Thursday, Scotland Yard said, before the radical preacher was arrested.
Another residential home and a business were also searched on Thursday, while a search on a third property is ongoing, the spokesman said.
The searches were carried out in connection with ongoing inquiries by the Counter Terrorism Command, he added.
No arrests have been made in connection with the police investigation.
More top news
Marks and Spencer will become the first UK retailer to add vitamin D to its entire packaged bread range.
An over-the-top 80's action movie parody featuring kung fu Hitler and a David Hasselhoff soundtrack gets almost four million views online.
The government is treating the fight against obesity as a priority, as a new report cautions that one in five cancer deaths is caused by it.