Chief Insp Graham Armitage, of West Yorkshire Police, is heading the massive search for the missing nine-year-old, which involves hundreds of police officers and 16 sniffer dogs.

He said: "It is the biggest missing person enquiry I have been involved in and I have 28 years of service."

He said across England, Wales and Scotland there were 27 victim recovery dogs trained to find bodies or blood - and this investigation was using 16 of them.

The dogs have come from forces as far afield as Surrey and Strathclyde.
Chief Insp Armitage said the dogs were trained to find victims "in whatever form the victim is".

He said: "We would like to find Shannon alive, obviously, but we have got to consider all options and victim recovery dogs will find all things from an alive person to drops of blood."

Det Supt Andy Brennan, who is in charge of the overall police operation, said the police were more than two-thirds of the way through searching 3,000 houses of interest in the Dewsbury Moor area.

He said: "Some properties will take longer than others and that's the people who may be of interest to us, as you may imagine."

He said open areas such as Crow Nest Park, the Spen Valley Greenway and Jessop Park in Batley had also been searched.