The Spider Man actor's house in Rome, Italy, was robbed by burglars who used ropes and mountain-climbing equipment to lower themselves down from the roof to get into the flat on Sunday night.
A friend of the actor and his wife Giana Colagrande said police were alerted to the break in via an alarm system.
Initial reports from Rome claim $4,200 worth of goods have been taken from the property, although a representative for twice Oscar-nominated Willem said the figure was closer to $3,000.
A police force source told the New York Post newspaper the items taken include jewellery, but they are unsure if anything else is missing.
They said: "We are waiting for the owner to return to draw up a full list."
Willem, 55, usually splits his time between homes in Rome and New York, but wasn't in the country at the time of the break in, as he is filming Odd Thomas in New Mexico.
A friend of the actor and his wife Giana Colagrande said police were alerted to the break in via an alarm system.
Initial reports from Rome claim $4,200 worth of goods have been taken from the property, although a representative for twice Oscar-nominated Willem said the figure was closer to $3,000.
A police force source told the New York Post newspaper the items taken include jewellery, but they are unsure if anything else is missing.
They said: "We are waiting for the owner to return to draw up a full list."
Willem, 55, usually splits his time between homes in Rome and New York, but wasn't in the country at the time of the break in, as he is filming Odd Thomas in New Mexico.
