Missing schoolgirl Alice Gross has sparked the largest search operation since the 7/7 bombings in the capital, the Metropolitan Police said.

Alice, 14, was last seen by her family at 1pm on Thursday, August 28 when she left her home in Hanwell and said she would return later that evening.

She was seen on CCTV walking along the Grand Union Canal towpath near the Holiday Inn, Brentford Lock, at 2.23pm the same day, heading toward the River Thames in Kew. At 3.45pm, she was seen walking along the same part of the towpath in the direction of Hanwell.

She has now been missing for 24 days.

Scotland Yard said nine square miles of open land and 3.4miles of canals and rivers had been searched by 600 police officers including specially trained search officers, divers and police dogs from eight different forces – leading to the biggest hunt for information since the terrorist attacks in London in 2005.

More than 630 phone calls have also been taken by investigators.

Latvian convicted murderer Arnis Zalkalns, 41, also from Hanwell, has been named as a suspect into the disappearance after he went missing on September 3.

Detective superintendent Carl Mehta, said: "Our thoughts continue to go out to Alice's family as our search continues in a bid to find her.

"I would like to thank the local community who have shown great support to the search effort and police investigation so far.

"Our officers are working through the weekend - carrying on those searches. We will not stop our hunt for Alice.

"Whilst we have already seized many hundreds of hours of CCTV we still need the public's help.

"If you are a shop owner, have CCTV at your home, or were out filming in the areas of Ealing and Hanwell and have footage from the afternoon of Thursday, August 28 when Alice was last seen, and right up to September 3 when Arnis Zalkalns was last seen, then please get in touch with us."

Scotland Yard have insisted there is no evidence to suggest that Alice, who suffers from anorexia, has come to harm.

A reward of up to £20,000 is being offered for anyone who has information that leads to Alice being found.

Anyone with information should call the incident room on 020 8358 0100, or call Crimestoppers anonymously on 0800 555 111.