Ten of the portraits featured famous athletes of the 1970s. The other was of Weisman. Some of the other sporting greats included golfer Jack Nicklaus, soccer star Pele and figure skater Dorothy Hamill.
A $1 million reward was being offered for information leading to the return of the artwork.
The editioned prints were on display in Weisman's dining room and his house was locked up. It wasn't clear exactly when the silk screen paintings were taken or how the thieves got into the home.
The theft was discovered by the family's longtime nanny who arrived at the home to find the large prints missing from the walls. She immediately went to a neighbor's to call police, Sommer said.
"This was a very clean crime," Sommer said. "(The home) wasn't ransacked."
It wasn't known exactly how much they were worth but Weisman tried to sell the collection in 2002 for $3 million.
Weisman's home contained other valuable artwork but the rest of his collection was untouched.
"For some reason they had an interest in this collection," Sommer said.
A neighbor saw a maroon van in the driveway of Weisman's home around the time of the robbery, and police are seeking more information about that, Sommer said.
Weisman declined to comment about details of the case when reached by The Associated Press on Friday.
Detective Don Hrycyk said the weeklong delay in announcing the theft was to allow detectives to confirm the reward and gather descriptions and photographs of the missing artworks.