The wife of an Indian-born lottery winner who was poisoned with cyanide said she was devastated by his death and cannot believe her husband could have had enemies.

With no signs of trauma and nothing to raise suspicions, the sudden death of a Chicago man just as he was about to collect nearly $425,000 in lottery winnings was initially ruled a result of natural causes.

Lottery ticket-holders in Illinois, Kansas and Maryland each selected the winning numbers for the world record-breaking $640m Mega Millions jackpot, officials have said.