Fatal blaze at former Lincoln Co-Op 'unexplained'
A fire in which a 17-year-old man died is currently being treated as "unexplained".
The blaze in De Wint Avenue, Lincoln, was at a former Co-op supermarket, which has flats above, at about 16:30 GMT, on Monday.
A woman and two men were also taken to hospital for minor injuries.
Det Insp Mark Blackbourn said: "We are exploring a number of possibilities and for that reason are currently treating the fire as unexplained."
He added: "This is a very traumatic and clearly tragic event for the family involved.
"For this to happen at any time of the year is devastating, but particularly so at Christmas time. Our thoughts are very much with them."
Lincolnshire Fire and Rescue said 50 firefighters were at the scene at the height of the blaze.
An eyewitness told BBC Radio Lincolnshire: "I've never seen anything like it... like a great big ball of flame, the decorations had gone up, there was black smoke everywhere, it was awful.
"I just think it's terribly sad, especially at this time of the year.
"It's sad not just for the family but the whole community is shocked."
A post mortem examination is yet to be carried out and no or formal identification of the victim has been made.
About £8,000 has been raised online to help the family who lived in the property.