The Tokyo Metropolitan Police Department has launched an investigation into political group Tsubasa no To on Monday over alleged campaign obstruction activities in the April 28 Lower House by-election vote in Tokyo.

MPD investigators raided the party’s headquarters in Tokyo’s Chiyoda Ward, as well the homes of party leader Atsuhiko Kurokawa and Secretary-General Ryosuke Nemoto.

The group is suspected of interfering with the campaign activities of by-election candidates in Tokyo’s No. 15 district — corresponding to the city’s southeastern Koto Ward — in violation of the election law.