Labor authorities have referred to prosecutors the operator of a Japanese language school in Miyazaki Prefecture, suspecting it of forcing Indonesian students to work at care facilities owned by the same company.

Additionally, documents related to Yutaka Shimizu, 70, the head of the group that runs Houei International Japanese Language Academy, and four others were also sent to prosecutors Thursday for their roles in allegedly forcing six Indonesians into effectively unpaid work between December 2015 and last June.

The students were allegedly forced to use their wages to cover tuition, a local labor standards inspection office said.

Authorities deemed the Miyakonojo, Miyazaki Prefecture-based school’s educational program and labor requirements as intertwined.

The school teaches Japanese to students from across Asia who are interested in the medical and welfare fields.

A lawyer representing the school operator released a statement maintaining that the company was not engaged in any illegal activity.

The company has been providing “working opportunities for students who wish to work,” it said, noting vocational experience gained at welfare facilities is crucial to the students’ studies.