Police have explained more about the 'blue material' that sparked excavation work at a Gloucester cafe as part of a decades-old investigation into a missing schoolgirl.

The search for human remains under The Clean Plate was triggered by what appeared to be an image of 'fabric' seen with ground-penetrating radar.

The Southgate Street cafe has been linked with the disappearance of 15-year-old waitress Mary Bastholm, who worked there, and serial killer Fred West, who was a regular customer there.

Gloucestershire Police said today they had found "no human remains or items of significance", at a cost of about £55,000, but with additional invoices yet to come it could be in the region of "£60,000 or £70,000".

Mary went missing on January 6, 1968, and was last seen at a bus stop in Bristol Road.

She was wearing a blue and white dress, a blue coat and was carrying a blue bag the day she went missing.

An ITV documentary film crew making a Fred West documentary explored the Clean Plate's basement floor.

After drilling in to the ground an endoscope, the film crew captured an image of what appeared to be 'blue material'.

The police's forensics team began excavating the cafe on Wednesday May 19 and found no such material.

What could it have been?

The belief is that image was of either "detritus or debris" which came from drilling into a pipe below, mistakenly identified as a fabric in the endoscope picture.

Speaking outside the police HQ in Quedgeley, ACC Craig Holden said: "The blue material photographed on an endoscope camera by the TV production company was not identified, but we did establish it was likely to be connected to a buried pipe.

"That pipe [which was not blue] was recovered and excavations went beyond the original endoscope depth.

"We believe that the drilling may have gone through the pipe and created some sort of detritus or debris, which is what the endoscope picked up.

"When we looked, we didn't see anything blue, so what we believe is that the imagery has given the impression of something blue.

"We've eliminated that whatever it was that could have been interpreted as blue in that imagery from our investigation."

Crime Scene Coordinator Martin Cuffe said: "The presence of blue material was quite a key fact in the early stage of the investigation and shaped part of the decisions for why we were going to perform this excavation.

"During all the work we've done we haven't identified anything that we'd describe as blue material consistent with an item of clothing.

"There is a possibility that the blue colouration that was seen on the endoscope might be the result of physical damage to one of the newer pipes that were installed as part of the installation of the toilets.

"When you look at the centre of them and shine quite a direct white light source on them, they do seem to give a blue colouration, and that does seem to be quite consistent with what we've seen on the images taken by the production crew."

Read more stories here:

Maternity unit worker thrown off bus for breast feeding

Police search of Gloucester cafe for missing Mary ends