Police investigating the deadly July bombings on London's transit system searched properties Friday in the northern city of Leeds (search), home to three of the suicide attackers.

Anti-terrorist officers were searching a combination of residential and business premises, together with local officers from West Yorkshire Police, said Scotland Yard (search) police headquarters in London.

"Searches remain ongoing. No arrests have been made," a statement from the London force said. "This is in connection with the terrorist attack in London on July 7."

Three of the four bombers suspected of carrying out the bombings lived in and around Leeds, 200 miles north of London. The attacks killed 52 people on three subway trains and a double-decker bus.

Hasib Hussain, 18, from a suburb of Leeds, blew himself up in a double-decker bus at Tavistock Square (search) in London. Shahzad Tanweer, 22, died in a blast on subway train near Aldgate station and Mohammad Sidique Khan, 30, blew up a bomb at the Edgware Road subway station.