Japan's leading advertising agency, Dentsu, says labor authorities have told it to end the excessive overtime worked by some of its employees.
Dentsu officials say the local labor standards inspection office in September told the firm's Tokyo head office to rectify the situation.
They say inspectors found that four Dentsu employees last year worked far longer than overtime limits agreed by the company and its labor union.
The officials say the inspectors determined the practice violated the Labor Standards Law.
At least one of the employees reportedly put in 156 hours of overtime a month, more than twice the agreed ceiling.
The officials say that in six cases employees failed to hand in applications to extend their overtime hours.
In 2017, Dentsu was found guilty and fined for overworking its employees after a 24-year-old new recruit committed suicide two years previously. Her case was ruled as death from overwork.
The latest move by the labor inspectors comes as the advertising agency says it is working to correct the situation under a program drawn up after the suicide case.