Firefighters were called out at 00.31 during the early hours of Tuesday morning to a fire involving a shed next to a house on McNeill Avenue, West End, Crewe.
When they arrived crews found the shed was on fire and that two adults and three children had managed to get out of the house safely.
Firefighters wearing breathing apparatus used hose reel jets to tackle the blaze.
One appliance from Crewe and one from Nantwich attended the scene.
A joint investigation between fire investigation teams and Cheshire Police has now been launched to find the cause of the blaze.
Cheshire police had CID at the scene, the police helicopter was also scrambled to the scene at around 04.20 due to reports of a possible arson suspect being seen in the area
If you have seen anything suspicious please call DC Kent on 101 quoting incident number 1070
If anyone has any other information that may help with this investigation please call Crimestoppers on 0800 555 111 or the police on 101