ROTTERDAM (CNN) -- Paintings by famous modern artists disappeared from an exhibition in the Netherlands in a predawn art heist Tuesday, shutting down an exhibition in the Kunsthal Rotterdam, where works by Pablo Picasso, Vincent van Gogh, Andy Warhol and Claude Monet are on display.
Seven works of "considerable value" disappeared in the museum theft, spokeswoman Mariette Maaskant said on Netherlands public radio.
"Initial investigations show the burglar was well prepared," police said in a statement.
Rotterdam police said evidence has been secured and they are speaking with potential witnesses. Investigators are also looking at security camera footage.
The paintings include Pablo Picasso's "Tete d'Arlequin"; Henri Matisse's "La Liseuse en Blanc et Jaune"; and Claude Monet's "Waterloo Bridge, London" and "Charing Cross Bridge, London," Rotterdam police said.
The other three were Paul Gauguin's "Femme devant une fenêtre ouverte, dite la Fiancee," Meyer de Haan's "Autoportrait" and Lucian Freud's "Woman with Eyes Closed."
The Kunsthal's alarm system went off shortly after 3 a.m. local time, alerting the exhibition hall's private security detail. When security staffers arrived by car, they saw that the paintings were missing, Rotterdam police spokesman Roland Ekkers said. They informed police, who started an investigation.
The works belong to a private collection that is being shown for the first time to the public, according to a Kunsthal statement.
The Triton Collection has taken 20 years to assemble and includes more than 150 works of modern art from the "late nineteenth century to the present day." It spans art movements from impressionism and expressionism to cubism and constructivism.
Its roster of artists boasts the names of Marcel Duchamp, Piet Mondriaan and George Braque, to name just a few.