Four more people have been arrested in connection with a national investigation into high-value museum thefts.
A 30-year-old man and two 17-year-old boys were arrested in London, while a 37-year-old man was arrested in Hull.
All four are being held on suspicion of conspiracy to burgle.
The latest arrests come a week after 20 people were arrested following a series of dawn raids across England and Northern Ireland.
The 18 men and two women have since been bailed until January.
Chinese artefacts and rhinoceros horn were targeted in six incidents - two thefts and an attempted theft from Durham University Oriental Museum and further incidents at Gorringes Auction House in East Sussex, Norwich Castle Museum in Norfolk and the Fitzwilliam Museum in Cambridge.
A man's due to appear in court this morning charged over the attempted theft of a rhino horn from Norwich Castle museum.
A curator at the museum managed to foil the attempted theft back in February.
Rhino horns are now so valuable the museum has replaced it with a replica.
Patrick Keily from Bow in East London is due to appear at Norwich Crown Court.
A rhinoceros head will return to the Castle Museum in Norwich 8 months after thieves tried to steal it for its horns.
Staff foiled an attempt to steal the 19th century African black rhino head from the museum in February. It was valued at half a million pounds but now, the horns, which have a street value higher than gold, have been professionally removed and replaced with replicas.
Security has been stepped up at Norwich Castle Museum after a number of items celebrating the life of the Norfolk naval hero Lord Nelson were taken.
The news comes at a time the museum's displaying an Italian masterpiece worth £100 million.
Police are reviewing CCTV and the National Security Adviser for the Arts Council is reviewing the museum's security arrangements.
The theft was noticed by an off-duty police officer who saw the cabinet which housed the objects had been tampered with.