By . Arthur Martin . PUBLISHED: . 04:54 EST, 10 September 2013 . | . UPDATED: . 06:04 EST, 11 September 2013 . Travellers were arrested in dawn swoops across the country  yesterday on suspicion of stealing more than £20million of jade  artefacts and rhino horns from museums. Police believe the items may have been stolen to order for Chinese collectors. Hundreds of officers from 26 forces arrested 17 men and two women in simultaneous raids. Detectives suspect they may be linked to the notorious Rathkeale Rovers gang that has burgled up to 100 museums across Europe since 2011. Scroll down for video . Raid: A Cottenham travellers' site was targeted in connection with thefts on museums and auction houses . The gang, which hails from an Irish traveller community in Limerick, steals artefacts for black-market dealers in the Far East. Yesterday’s arrests were in connection . with six burglaries at museums and an auction house over four months . last year. The travellers and their associates are suspected of stealing . 18 Chinese jade artefacts worth up to £18million from the Fitzwilliam . Museum in Cambridge in April. They are believed to have been sold on to Chinese collectors and have not been recovered. The suspects are also being questioned . about three break-ins at Durham Museum, one at Gorringes auction house . in East Sussex and one at Norwich Castle Museum. Horns from stuffed . rhinos were  stolen from the museums. Dawn: The Smithy Fen site was targeted with connections to the Fitzwilliam Museum robbery . Nationwide: 19 people in total have been arrested - 17 men and two women - including three men from Northern Ireland . Hunt: Rewards have been issued for the £15million worth of treasure plundered from the Fitzwilliam Museum . Organised: Soca and officers from 26 police forces are involved in the nationwide operation . Questions: Investigations are still going on across the country in relation to the spate of robberies across four months in early 2012 . Crackdown: The men arrested at the Cambridgeshire traveller site were aged 24, 41, 44 and 56 . Rhino horns are ground down and used . as medicine in the Far East. They have become so sought after that they . are worth more to smugglers than drugs or diamonds. Yesterday’s raids were on camps and . houses in London, Sussex, Cambridgeshire, Essex, the West Midlands, . Nottingham and Ulster. The operation was led by Cambridgeshire Police, . who arrested four of the men at the Smithy Fen travellers’ camp in . Cottenham. 'Pan-European': Further arrests in Wolverhampton were part of the operation that police say is working with forces abroad . Major: Operation Elven has been launched to recover items stolen from museums and involves raids like these in Wolverhampton . Thorough: A 32-year-old man was arrested in the West Midlands as part of the raids . Investigation: Police raided properties and garages early this morning . Recovered: Northern Ireland Garde officers remove items from a house during raids in the Rathkeale and Raheen areas of Limerick and in Newmarket in Cork . International: Garda sources said the raids were in connection to wider investigations into the theft of rhino horn . Connected: One man was detained at the Castle Street Rug Shop not far from the Belfast city centre in a raid police said was connected to museum thefts in England . Hidden: Several items were removed from the Belfast shop by a specialist search team . Target: Durham University's Oriental Museum was one of the institutions affected in last year's spate of robberies . Raid: Thieves chiselled a 2ft-by-3ft hold in the wall of the Oriental Museum of Durham University in April 2012 . Ransacked: After working at the wall for 40 minutes, it took the robbers just a minute to take Chinese artefacts from the museum . Jade: A 'recumbant buffalo' and an 'imaginary beast', two statuettes stolen from Cambridge's Fitzwilliam Museum in April 2012 . Reward: Police are still searching for many of the artefacts that were stolen . Antique: The Chinese artefacts date back to the Qing dynasty . Dishonour: A mourning ring worn by Admiral Lord Nelson's family after his death at the Battle of Trafalgar in 1805 and thought to be worth £25,000 was one of the items stolen from Norwich Castle Museum . Break-in: Thieves stole 18 items of Chinese art from the Fitzwilliam Museum in Cambridge in April 2012 . Eighteen of those arrested were held . on suspicion of conspiracy to burgle. A 54-year-old woman arrested in . London is suspected of perverting the course of justice and assisting an . offender. Chief Constable Mick Creedon, of the . Association of Chief Police Officers, which has set up a task force to . crack down on ‘heritage crime’, said: ‘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.’ Eight people have been jailed for a . total of more than 40 years for their roles in last year’s break-ins. They include three men and a 15-year-old boy convicted of  conspiracy . to burgle after the raid on the Fitzwilliam Museum. Cambridge Crown Court heard it was . unlikely the men knew the true value of the items, which were sold on to . rich Chinese collectors.
Four men arrested this morning at Smithy Fen travellers' site in Cottenham, Cambridgeshire . Total of 17 men and 2 women arrested from across London, Cambridgeshire, Sussex, Essex, West Midlands and Nottingham . Police from 26 forces and Serious Organised Crime Agency execute dawn raids as part of Operation Elven into six museum and auction house break-ins last year . Robberies at Durham University Oriental Museum, Gorringes Auction House, Norwich Castle Museum and Fitzwilliam Museum over four months in 2012 . Thefts and attempted thefts targeted items belonging to Admiral Lord Nelson, rhino horn and Chinese jade .