The labor ministry referred advertising agency Dentsu Inc. and one of its executives to prosecutors on Wednesday on suspicion of having a 24-year-old employee work illegally long hours, resulting in her suicide.

The decision by the Health, Labor and Welfare Ministry came unusually fast after the ministry raided the advertising giant on Nov. 7 following the overwork-related suicide of Matsuri Takahashi, who killed herself in Tokyo on Christmas Day last year.

The executive who was referred to prosecutors was Takahashi's supervisor.