Japanese officials have raided several offices of Dentsu as part of a widening investigation into working practices at the business following the highly-publicized suicide of an employee last December.
An investigation into that case attributed the death of the 24-year old to overwork, sparking a bout of soul searching at the agency and a wider police probe into its terms of employment.
In a sign of how seriously authorities are treating the case dozens of labour ministry officials visited Dentsu’s Tokyo headquarters early on Monday morning with parallel raids taking place in Osaka, Kyoto and Nagoya.
This follows a similar raid on Dentsu's Tokyo head office last month.
Dentsu has been embroiled in a PR crisis of its own making since news of the scandal first broke, with reports suggesting that the unnamed employee had worked 105 hours of overtime in October 2015 – despite or perhaps because of suffering from severe depression.
Japanese culture places heavy emphasis on a strong work ethic but it is feared that this may have been taken too far by some companies who disregard the wellbeing of their workforce. The problem has become so acute that death by overwork has even been given a name in Japan - Karoshi.
Dentsu, the world’s fifth largest advertising firm, is currently undertaking its own internal investigation and has vowed full cooperation with the authorities. It could face criminal charges if the practices are found to be widespread.