Unanswered Questions at the Kunsthal ROTTERDAM - It's back to the business of fine art for the Kunsthal, which reopened Wednesday with new paintings replacing the seven that were stolen during the early morning Tuesday. An emergency back door - facing a museum park - still bore dark marks and the neat labels of detectives investigating the crime with the suspicion that the criminals had entered there. The police announced that they were following up on more than 30 tips and examining surveillance videos. Visitors seemed undeterred by the art theft; on Wednesday afternoon a mix of students and older people were viewing the collection on loan from the Triton Foundation to the Kunsthal. Museum officials are still gamely trying to celebrate the institution's 20th anniversary, making an effort to avoid dwelling on the theft. They refused to identify the new works, or show where the old works had hung. "Seven works were stolen and there are seven new works from the same foundation," said Mariëtte Maaskant, a spokeswoman for the museum. Nor would they reveal the value of the stolen paintings, including works by Picasso, Monet and Matisse, perhaps a lesson from other museums that have suffered thefts. By avoiding giving a value, it makes it more difficult for the thieves to calculate a standard black market price of 10 percent. Helma Prens, a visitor at the museum, still found cause to celebrate her 71st birthday with a tour of the remaining art. "Maybe they didn't know the real value of this, not just the money, but the cultural value," said Ms. Prens about the thieves. I hope they find it, and that we find the real story. It could be a long wait. The Tate Gallery endured more than eight years of waiting and cloak-and-dagger negotiations before recovering two Turner paintings that were on loan to a museum in Frankfurt and were stolen in 1994. Earlier this year, Serbian authorities in Belgrade recovered "The Boy in the Red Vest," by Paul Cezanne, which was stolen more than four years ago in Zurich from the E.G. Buehrle Collection along with three other paintings by three masked robbers. Four men were charged in September, one of them a Serbian baker who was arrested while working the night shift.