Officers are appealing for information and video footage following a fire that occurred on Storey Square in Barrow on 1 June at around 6pm.
A joint investigation has been launched.
Two men were taken to hospital with serious injuries and third man was taken to Furness General Hospital for smoke inhalation.
A 57-year-old man was arrested on suspicion of arson with intent to endanger life, he remains in police custody.
Officers are aware some members of the public were filming at the scene and may therefore have video footage which could assist the investigation.
Anyone with video footage or information relating to this incident is asked to report this online at www.cumbria.police.uk/report-it, quoting incident number 193 of 1 June 2023.
You can also phone on 101.
Alternatively, you can contact Crimestoppers, anonymously, on 0800 555 111.