A number of individuals are thought to have been involved in the break-in at the museum in Trumpington Street at approximately 7.30pm on Friday, April 13.
Police, alerted by the museum's alarm system, have carried out forensic examinations following the burglary and CCTV footage is being examined.
The 18 items stolen are mostly Ming and Qing dynasty jades and had been part of the museum's permanent collection for over 50 years.
Asian art specialist John Axford of Salisbury auctioneers Woolley & Wallis, who had recently inspected the items during a visit to the Fitzwilliam, told ATG that values ranged from around £100,000 to about £3m for several individual pieces that had been stolen.
Police patrols have been stepped up in the area of the museum since the burglary while a Fitzwilliam spokesman said a thorough review of security measures was also under way.
Det Ch Supt Karen Daber, who is leading the investigation, called Operation Tundra, said: "The items stolen are very valuable and are of great cultural significance. We are following up a number of inquiries but we also need the help of the public.
"Anyone with information should contact police on 101 or Crimestoppers, anonymously, on 0800 555111. Information can also be reported by email at firstname.lastname@example.org"
DCS Daber has ruled out the possibility of an 'inside job' but would not be drawn on speculation that the robbery may be linked to a similar theft which took place earlier this month at Durham University, although she said officers were liaising with Durham police.
In a well-planned operation, thieves chiselled into the university's Oriental Museum through an outside wall on April 5 before stealing a Qianlong jade bowl and a Qianlong porcelain figure group with an estimated combined value of £1.8m.
The damage and subsequent investigation forced the museum to shut for many days.
The Fitzwilliam will take some heart in the knowledge that those two objects have since been recovered by police and five people arrested in the West Midlands in connection with the theft. All were bailed pending further inquiries.