Tokyo: The Japanese police investigating a so-called "Black Widow", who could be behind the deaths of six partners, have found traces of cyanide in soil from her pot plants, reports said on Friday.
Chisako Kakehi, 68, who was arrested last month on suspicion of murdering her 75-year-old spouse, received JPY one billion (USD 8.5 million) in insurance and other payouts over 10 years following the deaths of husbands and lovers, media have said.
Police believe she killed Isao -- her fourth and most recent husband -- with cyanide in December last year.
Investigators who tested plant pots she had taken to a recycling centre about six months after her husband died discovered a bag at the bottom of a planter. Lab results showed the presence of cyanide compounds, Kyodo News and other media reported.
Since the death from illness of her first husband in 1994, Kakehi had reportedly been involved with more than 10 men, of whom six had perished.
Reports say that most were elderly or ill and she was deliberately targeting unattached wealthy men as part of a plan to get insurance payouts or to inherit their assets.
Kakehi has denied murder.
Cyanide was found in the body of at least one of the men she was involved with before her recent marriage.
Police who earlier raided her home in Kyoto found traces of cyanide in the rubbish, media said.
They also found paraphernalia for administering drugs and medical books at an apartment she kept south of Kyoto.