Arsonists caused thousands of pounds worth of damage when they torched a charity shop in Driffield.
Police are investigating the blaze at Barnardos on Middle Street South, which gutted the shop and caused £3,000 damage to the building and its fixtures, fittings and stock.
CCTV images show a number of youths in the area when the fire began at around 1am on Tuesday.
It is believed the fire began at the rear of the store after a hole was kicked through boarding behind a doorway annexed by an alley to a storage area.
Officers also found abusive graffiti sprayed on the building.
The alarm was raised by Liam Barwick, 21, and his friend Jamie Robson, 17, who were out walking at 1.30am when they saw smoke which they at first thought was fog.
Liam, who lives in a flat on Riverhead, said his first instinct was to go to the flat next to the shop to see if anyone was inside, while Jamie rang the emergency services.
He said: “When there’s something like that happening you can’t just stand back and watch it. As I rang the doorbell to the flat there were two lads in their twenties coming down the stairs. They said they could smell smoke and I said they had to get out becasue there was a fire.
“After we got them out we went to the other side of the road and that’s when we saw the blue-flashing lights of the emergency services.”.
Barnardos spokeswoman Jo Hewitt said the store had been gutted.
“We are very upset about it. We have got a really loyal staff, volunteers and customers in Driffield.
“It is heartbreaking when you think of all the time and effort volunteers and customers have invested in the shop.”
Three fire tenders were despatched to the scene to fight the blaze - two from Driffield and one from Bridlington.
A spokesman for Humberside fire and Rescue Service said firefighters had tackled the blaze using two hose reels, one main jet, a short extension ladder, two Thermal Image cameras and sex sets of breathing apparatus.
Police have launched an appeal for witnesses. Anyone who saw anyone in the area at the time of the fire, or anything suspicious, is asked to call officers on 101 quoting log number 24 of June 10.