Eight churches and chapels have been targeted by criminals over the last five weeks.
St Margaret's Church, Blackwood, was broken into with Â£10,000 in damage caused between 14-15 June.
Cash was also stolen from Crosskeys Pentecostal Church, Crosskeys, and St David's Church, Pengam. Extra patrols have been put in place, said police.
Entry was forced at St Catherine's Church, Crosskeys; St Thomas' Church, Cefn Fforest; Horeb Baptist Chapel, Gelligaer; and Caersalem Chapel, Aberbargoed - but nothing was taken.
Det Insp Amanda Thomas said "unscrupulous attacks of damage and theft will not be tolerated".
Gwent Police are investigating after a spate of burglaries at churches and chapels in Caerphilly county.