(CNN) -- A magazine publisher, a photographer and a regional newspaper are under investigation in France for invasion of privacy over the publication of vacation pictures of Catherine, Duchess of Cambridge, authorities said Thursday.
An unnamed female photographer was placed under investigation on April 2, according to Caroline Chassain, spokeswoman for the Nanterre prosecutor.
Mondadori France, publisher of the French edition of Closer magazine, was placed under investigation on April 4, and La Provence, a regional daily newspaper, was placed under investigation Monday.
Topless photos of Catherine, wife of Britain's Prince William, appeared in the French edition of Closer. Photos of her in a bikini were published in La Provence in September.
The grainy topless pictures, shot from a distance, were taken while Catherine was sunbathing in private during a vacation at a chateau owned by William's uncle in Provence, southern France.
Closer and La Provence declined to comment on the investigation.
The lawyer acting for the Duchess of Cambridge in France, Aurelien Hamelle, also declined to comment.
Catherine is expecting her first child with William, who's second in line to the British throne.
Closer was fined last September for publishing the topless photographs and ordered not to distribute the magazine in print or online.
A French court also ordered the magazine to hand over the original photos to the royal family within 24 hours of the ruling.
The photographs subsequently appeared in outlets in other countries, including Denmark, Italy and Sweden.
No media outlet in Britain published the images.