A joint investigation with the fire service was launched after reports of the fire at Southern House in Halliwell at around 1.20am this morning.
A 28-year-old man has since been arrested on suspicion of arson and remains in custody for questioning.
Thankfully no-one was injured.
Details can be reported to police by calling 0161 856 5757 quoting incident number 99 of 09/05/19.
Information can also be given anonymously to the independent charity Crimestoppers on 0800 555 111.