Mid Ulster District Commander Superintendent Michael O’Loan said: "We are continuing to search for 21-year-old Lee Johnston, from the Coleraine area, who we are treating as a high risk missing person.
"Lee was first reported missing to police on Friday evening, 13th October and we are becoming increasingly concerned about his safety. It is completely out of character for him to not be in contact with his family, who are being supported by specialist officers during this worrying time.
"We have launched a criminal investigation into his disappearance to support the missing person investigation. Two people, a woman aged 31 and a man aged 33, who were arrested have since been released on police bail pending further enquiries.
"Lee has links to the Coleraine, Ballymena, Limavady and Cookstown areas.
"I am appealing directly to Lee to make contact with the police, family or friends so that we know you are safe and well.
"I am also asking the public to contact us if they have seen Lee. I know he was last seen on Saturday, October 7th:
- At 4pm we believe his was in the Mullagh Park area of Maghera.
- We then have a confirmed sighting of him in a supermarket on the Orritor Road in Cookstown at approximately 4.52pm. CCTV shows him in the store and going through a checkout.
- We now have a new confirmed sighting of him in the area of Dunmore Crescent Cookstown at 5:24pm.
"Please look at the photograph of Lee. He has short brown hair, blue eyes and around 5 foot 9 inches in height, and was last seen wearing a blue hooded-top and tracksuit bottoms."
Superintendent O’Loan continued: "I am appealing to anyone who was travelling through the Mullagh Park area in Maghera between 3pm and 4pm on Saturday, 7th October to think if they saw Lee or anything unusual or saw following his visit to the supermarket after 5pm. If you did, please report it to police immediately.
I would also appeal to anyone with dash-cam, CCTV or mobile footage that could help our enquiries, to also make contact with police on 101, quoting reference number 1782 13/10/23.”
You can also contact the independent charity Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers.uk.org.