A 15-year-old boy is being questioned on suspicion of arson after a blaze at Manchester Dogs' Home which killed more than 40 dogs.
Firefighters were called to the scene in Harpurhey shortly after 7pm on Thursday when a fire broke out in a kennel section.
About 150 dogs were rescued and were being moved to the charity's sister home in Grappenhall, Cheshire.
Hundreds of residents flocked to the site in Moss Brook Road with dog blankets, cages and food, with some reportedly helping to save some of the animals.
More than 30 firefighters brought the blaze under control with damage caused to about a third of the kennels.
A joint investigation by Greater Manchester Police and Greater Manchester Fire and Rescue Service is under way as dampening down at the home continues.
Superintendent Marcus Noden said: "We are working closely with Greater Manchester Fire and Rescue Service to establish how this tragedy has occurred.
"We are in the very early stages of the investigation and have a young boy in custody, however we would ask if anyone was in the area and remembers seeing anything suspicious around the dogs' home that they call police and tell us what they know.
"As a dog owner myself I understand that many people will feel angry and upset about what has happened but I would ask that they let the police carry out their investigations and not take matters into their own hands.
"We have received an overwhelming response from the public and would ask if anyone wants to help they can make donations of food or bedding to North Manchester divisional headquarters on Northampton Road in Newton Heath."