The men, aged 24, 41, 44 and 56 were among 19 people snatched by police in dawn raids across the UK yesterday (September 10) and held on suspicion of conspiracy to burgle.Of those arrested 12 were still being held today by police as well as a 22-year-old man who was arrested later in London on suspicion of conspiracy to burgle.Hundreds of officers from 26 police forces and the Serious Organised Crime Agency (SOCA) are involved in the operation and searches are ongoing at The investigation involves hundreds of officers from 26 forces and the Serious Organised Crime Agency and relates to six crimes over a four-month period at museums and auction houses across England. Chinese artefacts and rhinoceros horn were stolen in five incidents - three at Durham Museum, Gorringes Auction House in East Sussex and the Fitzwilliam Museum in Cambridge. While much of the property was subsequently recovered, several high-value items are still missing. Chief constable Mick Creedon, lead for serious organised crime for the Association of Chief Police Officers, said: The series of burglaries last year had a profound effect on museums and similar institutions and we are committed to bringing all those who were involved in the conspiracy to justice. Many of the stolen Chinese artefacts are still outstanding and a substantial reward remains on offer for information which leads to the safe return of those priceless items. Anyone with any information should call Crimestoppers, anonymously, on 0800 555111.