The works are worth €3.5 million (US$5 million) and depict figures including a ballerina, a sparrow and a male nude, all designed in the rounded style of Botero's art, an official with the Carabinieri paramilitary police said.
The statues were stolen from Pietrasanta, a Tuscan town where Botero spends part of the year, said Lt. Angelo Murgia.
Sometime during the weekend, burglars forced the foundry's back door and then broke into a metal cupboard that housed the statues, each 50-70 centimeters (20-27 inches) tall and weighing 25-30 kilograms (55-66 pounds).
The works had been insured, Murgia said.
Barbara Lazzeri, the wife of one of the foundry's owners, said an alarm at the factory had not been activated, as it was often accidentally set off by animals, and that the break-in was discovered Monday when the business reopened after the weekend.
"There are pieces by other artists here, but they took only those by Botero," Lazzeri told The Associated Press by telephone from the foundry.
She and Murgia said the burglars seemed to be after Botero works, indicating the theft may have been commissioned.
Murgia said two other Botero statues, a rooster and a Colombian idol, were stolen from the artist's home and studio in Pietrasanta in 2006.
Botero, who was in New York, was told about the new theft on Monday.
"He was quite angry and stopped production of all his works," Lazzeri said. "He said he will continue to work in Pietrasanta only if the foundries are made secure."
Famed for his works on Colombian life, including images of the 40-year-old conflict in the South American country, Botero created controversy in recent years with drawings and paintings depicting abuse of prisoners by U.S. troops at the Abu Ghraib prison in Iraq.