Officers using specialist equipment are examining land around the Cariad Farm site in Marshfield, Newport.
The search - prompted by suspicion a body has been buried there - is expected to last for several days.
More top news
Wrexham man Christopher Matthew Griffiths has been jailed for cutting his dog's ears off. Traces of cocaine were found in the dog's urine.
Stephen 'Beano' Pike stabbed his neighbour Clint Simms on his doorstep in Ely, Cardiff. He was jailed for life at Cardiff Crown Court today.
Police appeal after a man sexually assaulted a teenage girl sat beside him on an Arriva train to between Cardiff and Pontypridd.