LONDON, July 8 (Xinhuanet) -- More than 50 people were killed and about 700 wounded in four blasts in central London on Thursday, Metropolitan Police Commissioner Ian Blair told a news conference on Friday.

    "There were more than 50 fatalities," said Blair, adding that among 700 injured people, 22 were in critical condition.

    Of the 300 people admitted to hospital on Thursday, about 80 remain, either convalescing after emergency surgery or too badly burned to return home, he said.

    The police chief said although two of the blast sites were still hard to assess, he did not expect the death toll to rise dramatically.

    But he said the final death toll was not yet known due to the dangers of reaching some of the underground blast sites.

    Meanwhile, London police said a massive intelligence investigation is under way to find those responsible.

    They were paying close attention to an Al Qaeda statement claiming responsibility for four bombs that killed at least 50 on the city's transport network on Thursday morning.

    "We obviously are aware of it -- what we cannot know is if it is real or disinformation," the city's police chief Ian Blair told reporters.

    He said "but we are taking considerable note of it."

    Meanwhile, British investigators scrambled on Friday to hunt down suspected al Qaeda bombers to stop them striking again.

    A day after four bombs tore through three underground trains and a red double-decker bus, commuters headed to work again on London's battered transport network on Friday.

    British Home Secretary Charles Clarke said Thursday looking forpotential bombers was like searching for needles in haystacks".

    The attacks -- which ministers said bore the hallmarks of the Islamic militant al Qaeda network -- were London's deadliest in peacetime and coincided with a summit of the Group of Eight (G8) top industrialized countries in Gleneagles, Scotland. Enditem