MILWAUKEE (CBS 58) -- Milwaukee police a fire they say was intentionally started inside an apartment building Friday, Jan. 16. 

Crews responded to the building just after 6:30 a.m. near Loomis and W. Fardale Avenue. 

Five people were taken to the hospital for treatment, according to MPD: a 27-year-old with life-threatening injuries, a 64-year-old and 18-year-old with serious but non-fatal injuries, and a 47-year-old and 9-year-old with non-fatal injuries. 

Police say they're looking for a known suspect. 

Anyone with information is asked to contact MPD at 414-935-7360, or to remain anonymous, call Crime Stoppers at 414-224-TIPS.