Agence France-Presse and the London newspapers The Independent and The Guardian report that the thefts are part of a wave of vandalism and burglary that have recently plagued the largest burial ground in the French capital.
Authorities estimate each of the missing busts to be worth between €5,000 and €10,000.
"We're dealing with a group theft carried out over a short period of time," said an unnamed source quoted in The Independent. "And there is without doubt a collector behind it. The pieces are almost never catalogued, and so it would be very easy to sell them on the black market."
With monuments to such revered figures as Oscar Wilde, Edith Piaf, Maria Callas and Jim Morrison, the Pre-Lachaise cemetery has long struggled with heavy traffic (now 2 million visitors a year) and persistent vandalism.
The Guardian quoted a representative for the Paris cemetery workers' union as saying, "20 or so wardens were not enough ... at a site whose five gates are open to the public, where the landscape is hilly and where someone can hide behind a cross or a tombstone, out of sight."