BERLIN (AP) — Police raided sites in Berlin and northern Germany on Wednesday in an investigation of three people suspected of forcing Vietnamese women who had been smuggled to Germany into prostitution.

The main suspect, a 43-year-old Vietnamese woman, was arrested at her apartment in Berlin. Police said the two other suspects are a 25-year-old woman from Vietnam and a 64-year-old German man, news agency dpa reported. The operation was the result of a year-long investigation.

Federal police said they searched eight properties in Berlin, Hamburg and the Baltic Sea resort town of Timmendorfer Strand. Around 160 officers took part in the raids.

Investigators believe the suspects employed the victims in nail studios and massage parlors and forced them into prostitution at those sites, at financial benefit to themselves, police tweeted.