Japanese police have arrested four people suspected of involvement in a financial fraud that has ensnared investors including Lehman Brothers, which is suing Marubeni for Y35bn ($324m) over the affair.

Police over the weekend arrested Shigenori Saito, former president of medical consultancy Asclepius; Yuzuru Yamanaka, former representative director of LTT Bio-Pharma; Shingo Yamaura, a former Marubeni employee; and Fumihiro Takahashi, president of a Tokyo-based building consultancy.