Punjab National Bank was defrauded of $1.77 billion in a scam perpetrated by Nirav Modi, a diamond trader, and his associates. Modi fraudulently obtained letters of undertaking from PNB to secure loans from other banks without providing collateral. The fraud was detected in January 2018 when PNB officials noticed fraudulent transactions were not recorded properly. The scam has significantly impacted PNB and other public sector banks through loss of funds and declining share prices. Investigations into the fraud are ongoing along with efforts to recover funds from Modi's seized assets.