A Metropolitan police spokesman said officers had completed their searches of all four properties today and no hazardous materials had been found.
More top news
The teenagers, aged 19 to 15, appeared in custody at Westminster Magistrates' Court on Saturday, supported by their families.
Labour must "broaden its reach" in order to win votes off the Conservatives, deputy leader Tom Watson has said.
Nicola Sturgeon said the London mayor's comments that likened Scottish nationalism to racism were a sign of 'desperation'.