An organised gang stole £100,000 worth of jewellery after targeting Asian families celebrating Ramadan and Eid.
The thieves are said to have waited until residents had gone to the mosque before breaking in.
Sussex Police believe one gang raided 12 homes in areas of Crawley including Broadfield, Tilgate, Langley Green and Pound Hill, in July and August.
Between £1,000 and £30,000 of jewellery was taken from each property.
Sgt Jim Collen said that it was thought that the gang identified potential targets by visiting homes and pretending to offer cavity wall insulation.
He said: "They are certainly conducting some kind of hostile reconnaissance and they are certainly taking advantage of their knowledge of the local community, targeting households when they know they are going to be vacant, and when they know there is going to be a window of opportunity."