Milan prosecutors investigating alleged worker exploitation in the supply chains of big name brands have requested documentation from another 13 fashion groups, according to reports on Thursday by Il Corriere della Sera and Il Sole 24 Ore confirmed by official documents.

The requests regard, in particular, the company's control systems for production contractors and sub-contractors.

Dolce&Gabbana, Versace, Prada, Gucci, Missoni, Ferragamo, Yves Saint Laurent, Givenchy, Pinko, Coccinelle, Adidas, Alexander McQueen Italia, and Off-White Operating have been asked for the documentation.

Milan prosecutors have staged a series of investigations in recent years into worker exploitation by companies active in Italy, including several multinationals and a number of top fashion brands such as Loro Piana, Valentino, Dior, Armani and, most recently, luxury shoemaker Tod's.