Japanese police were looking for traces of poison in the home of a woman arrested on suspicion of killing her husband, one of six men who have died while in a relationship with her over the past 20 years.

Police say they suspect insurance claims or inheritance money could be the motive for the killings.

Chisako Kakehi, 67, was arrested Wednesday in Kyoto prefecture after cyanide was found in the body of her 75-year-old husband, a senior official at the investigative department told The Associated Press in a telephone interview from Kyoto. He spoke on condition of anonymity, citing the pending investigation.

Kakehi has denied involvement in the deaths and has not been formally charged.

Her latest marriage lasted one month before her husband died in December.

Cyanide had also been found in the blood of a 71-year-old partner who fell while riding a bike in 2012, officials said. His death was initially attributed to a heart disease.

Kakehi had reportedly married three times and had relationships with three other men over the past two decades. All had died within a few years of marrying or starting relationships with her.

All the deaths occurred in the western Japan area, including Kyoto and Osaka.

On Thursday, police raided her apartment in Osaka following searches at her home in Muko city, and confiscated capsules and wafers to wrap powdered medicine as possible evidence, reports said.

Kakehi caught the attention of authorities after she called an ambulance to rush her latest husband to a hospital, saying he suddenly collapsed at home. An autopsy found cyanide in his blood, and investigators eventually ruled out a suicide, leading to Kakehi's arrest.

She was being questioned by the prefectural prosecutor before a decision is made whether to press charges.