A "warning shot" has been fired by South Wales Police Deputy Chief Constable Matt Jukes to those intent on causing grass fires across the region.
He told ITV News that he promises to take "robust action wherever possible" on those caught setting their communities alight.
The total number of grass fires dealt with by South Wales Fire and Rescue Service are up by nearly 200% on last year, new figures show.
More than 100 blazes across Rhondda Cynon Taf and Merthyr Tydfil have been reported to police since the beginning of March.
People starting grass fires should be locked-up Wales' Public Services Minister will be told later today