Hendon has been bombed for the second time in weeks
One person has been hurt in a blast at a north London postal sorting office where a bomb went off three weeks ago.
Police, including anti-terrorist officers, were called to the building in Hendon at 0153BST on Sunday.
One passer-by received minor injuries but did not need hospital treatment, a Scotland Yard spokesman confirmed.
Police have cordoned off the area and officers are working with ambulance and fire services.
A spokesman for Scotland Yard said that "relatively minor" damage had included broken windows.
He also confirmed that no bomb threat calls or warnings were made prior to the incident and no-one had claimed responsibility.
Scotland Yard's Anti-Terrorist Branch boss, Deputy Assistant Commissioner Alan Fry, is at the blast scene.
He told the BBC that about half a pound of explosives had been used in the latest Hendon incident.
The quantity used was "sufficient to cause serious injury or even death", he said.
Petrol station worker Ambalawanar Ahilan, who works in a BP garage close to the sorting office, said he heard a a "huge bang" at a round 0200BST.
He said: "It made me and a customer jump. I ran outside but couldn't see anything and within a couple of minutes police cars were rushing in.
"I was here when the last bomb went off and this one seemed louder."
Anti-terrorist officers have been on high alert over the bank holiday weekend as Saturday was the 20th anniversary of the death of hunger striker Bobby Sands.
A suspected terrorist bomb packed with high explosives blew out windows at the Hendon building in north London on 14 April.
The depot suffered minor damage in that blast.
The building is a small delivery office dealing
with mail for the NW9 area, and one of 100
similar-sized buildings in London.
-- Anonymous, May 06, 2001