The theft of a bronze sculpture by the Swiss artist, Alberto Giacometti, went unnoticed for days after the thief replaced it with a crude wooden copy.
German officials at Hamburg's Kunsthalle believe the sculpture was stolen on May 25 during the city's "Long Night of the Museums", when cultural attractions were open until three in the morning. But it took three days before a member of staff noticed the substitution.
"The culprit appears to have lifted a plexiglass cover from the free-standing case, replacing it with an inexact wooden copy that was undetected for some days," said Hamburg police spokesman Ralf Kunz.
The 32-centimetre tall sculpture, worth about SFr730,000 ($464,000), is one of six identical bronze sculptures created by the Swiss artist in 1956.
"It's one of my favourite pieces in the museum," said museum director, Uwe Schneede, "and I truly hope that we will get it back with the help of the public."
Over 16,000 people visited the museum during the night it was open, but police say it was possible the culprit was alone for a short time.
Meanwhile, a watercolour by the artist has fetched SFr118,000 ($75,350) at auction in Zurich - a record for a Giacometti watercolour.
The work, entitled "Near Florence", was bought by a Swiss bidder for double its estimate.
swissinfo with agencies