An “extremely distressed” family is asking farmers and landowners to check their property for a pensioner missing since Thursday.
Marion Scott, 83, of Acre Close, Market Rasen was last seen at her home at around 6.45pm on December 27.
Marion, known locally as Mary, has dementia, suffers from memory loss and can be confused.
Police and volunteers, including members of Lincolnshire Community Assistance Team, spent the weekend searching the area surrounding Market Rasen, including Willingham Woods, for Mrs Scott.
But officers say they feel they have now covered all the areas that Marion likes to visit locally and the areas where it is felt that Marian may have been capable of reaching.
Assistant Chief Constable Keith Smy said, “We are extremely worried about Marion Scott and are doing every thing we can to find her, naturally her family are very upset and concerned.
“I have been very impressed with the help we have received from many local residents and other volunteers who have turned out in great numbers to help us. I would like to thank them all for their efforts so far.
“We are determined to leave no stone unturned in our efforts to find Marion.”
In addition to the ground searches, a police helicopter with heat-seeking equipment has been used and social media has alerted members of Farmwatch and Neighbourhood Watch in the Rasen area.
Inspector Michelle McIlroy said: “We have a family liaison officer with Marion’s husband, Douglas who is obviously extremely distressed at his wife’s disappearance. “
Marion’s daughter Rebecca Ross, who lives in Rothwell, said the last sighting of her mother had been in Hainton and stressed she may not know her name or whereabouts.
She added: “It’s like living in a nightmare, we just don’t know where she is.”
Marion is described as around 5ft 4in tall, of slight build with short black hair. She was wearing brown cord trousers, grey slip-on shoes and a green top. It is thought she was wearing a pink jacket.
Call police on 101 or 999 quoting incident number 325 of 27th December.