Malaysia's anti-graft agency has confirmed former prime minister Mahathir Mohamad is being investigated in connection with a probe involving his sons. Both his sons have been served notices to declare their wealth as part of ongoing inquiries into offshore financial and business records. The probe comes amid a widening crackdown on graft involving prominent political figures. This includes those seen as allied to the 98-year-old former leader himself. Melissa Goh reports from Penang.