The move came after opolice searching for the woman who disappeared 43 years ago found nothing during an excavation of the garden at her former home.

She was last seen in 1969 at her home in Annan Glade, Motherwell.

The 34-year-old primary school teacher, known to friends as Evelyn, was married with two children, then aged four and 18 months.

Officers from Strathclyde Police were yesterday digging up the back garden of the property, but said last night that the search had "proved negative".

They also used specialist ground-penetrating radar equipment at the house and garden, but nothing was found.

A spokeswoman said: "An extensive search of the property at Annan Glade, Motherwell has been carried out utilising sensitive search equipment. This search has proved negative.

"The property has now been handed back to the householder, and the police are grateful for the assistance and co-operation provided."

Further searches will be conducted in the immediate area over the coming days and weeks, the force said.

It stressed that there would be no disruption to local residents.

The spokeswoman added: "This remains very much an active investigation."

Ms Ruffle was born in 1935 in Motherwell. She trained as a teacher at Craiglochart Training College in Edinburgh in 1953-56. She then took teaching posts in Singapore, Bournemouth and various schools in North Lanarkshire.

She was working at Cathedral Primary School, Motherwell when she went missing.

Superintendent Andy McKay said: "I urge anyone with information, no matter how small, to come forward."