Heather Mills-McCartney discovered the masterpieces were missing when she set off the burglar alarm after the codes had been changed, The Sun newspaper reported.
Police arrived at the ex-model's lodge on Sir Paul's sprawling estate in Peasmarsh, East Sussex, yesterday.
A Sussex Police spokesman said today: "There was no criminal offence. They have been advised to contact their solicitors. It's a civil matter."
According to The Sun, Sir Paul said he was taking the paintings - which included Renoirs and Picassos - because he was concerned about security at the lodge.
Photos of the couple's three-year-old daughter, Beatrice, have also gone missing, it was said.
Ms Mills-McCartney's friend told The Sun: "Heather can't believe things have got this bad."
A spokesman for Sir Paul declined to comment.
The 64-year-old and Ms Mills-McCartney, 38, announced in May that they were ending their four-year marriage.
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Sharon Ward, Halifax, Nova Scotia, Canada (29/12/2006 at 13:51)