11/08/2007 at 04:30 PM EST
Police raided Amy Winehouse's London house Thursday and arrested four men elsewhere in the same operation.
The troubled 24-year-old singer was not arrested, and police did not reveal why her house was targeted but noted, "Investigations are ongoing."
Officers from the Metropolitan Police Service were seen entering the back of Winehouse's residence in northwest London, according to local press accounts, which said Winehouse and husband Blake Fielder-Civil were not believed to be home at the time.
Four unidentified men ages 19 to 25 were arrested at addresses in east London on allegations of perverting the course of justice, police said in a statement.
Winehouse, who is appealing a pot bust in Norway
, surfaced last week at the MTV Europe Music Awards
, where she sang a low-energy "Back to Black" and offered a quiet "thanks" after picking up a trophy.
A rep for Winehouse had no immediate comment.