The players - named by officials as Takuya Hashimoto, Keita Imamura, Yuya Nagayoshi and Takuma Sato - are said to have headed into Jakarta in national team clothing following Thursday's 82-71 win over Qatar.
In a news conference, Japan chef de mission Yasuhiro Yamashita said the four "spent the night in a hotel with women", while Yuko Mitsuya, chief of the Japan Basketball Association, declared that further sanctions were likely to be forthcoming.
