Keela hit the headlines two years ago because she was earning more than her force's Chief Constable.

The South Yorkshire Police dog has already helped forces across the country, including working on the high-profile stabbing of pregnant mother Abigail Witchalls in Surrey, and was being hired out for £530 per day, plus expenses.

Back then she would have been earning almost £200,000 - around £70,000 more than her force's Chief Constable - if she worked every day of the year.

She has been trained to ignore decomposing body materials other than human blood.

And instead of barking when she smells blood, she has been trained to have a "passive" alert - freezing with her nose as near to the subject matter as possible without touching, to enable scientists to recover the sample quickly and efficiently.

This technique has saved time and money on major investigations.

She can search any area, including houses, cars, boats, both indoors and outdoors, and will lead her handler to spots of blood so small that humans cannot see them.

She screens textiles and can pick out traces of blood even after clothing has been washed many times or weapons cleaned.

When Keela was working on the Abigail Witchalls case she found eight piece of blood-stained clothing in just one day.

Now the dogs have been brought in to help after the police looking into her disappearance re-focused on the McCanns' holiday apartment.

Madeleine has now been missing for 99 days and police are increasingly desperate for any kind of breakthrough in her case - as are her parents Kate and Gerry, who are still in Portugal.

Both sniffer dogs are attached to South Yorkshire Police.

Eddie is a "victim recovery dog" who can detect blood and human remains.

Helpful hound: Eddie is to help in Madeleine search