A Japanese woman was arrested yesterday in connection with the death of her 75-year-old husband after traces of arsenic were found in his blood. 

A senior investigative official reported that 67-year-old Chisako Kakehi is suspected in the deaths of two other husbands and three partners over the past 20 years. 

The official spoke to the Associated Press under the condition of anonymity because the investigation is still pending. 

Kakehi's homes in Muko and Osaka were raided this week, and police found capsules and wafers used to wrap powered substances. Cyanide was also detected in Kakehi's disposed personal belongings. The items were taken as evidence, and Kakehi was placed under arrest. 

Kakehi had reported that her husband, Isao Kakehi, collapsed at home in December 2013, and suicide was ruled out. The couple had been married for one month. 

Sources say Kakehi attempted to purchase sleeping pills at a drugstore before her husband's death, but bought herbal drugs with similar effects when questioned about having a prescription. 

A 71-year-old partner of Kakehi's died in 2012 while he was riding a bicycle, and cyanide was also found in his blood. The death was initially attributed to a heart condition. 

The other husbands and partners all died within a few years of dating or marrying Kakehi, and all of the deaths occurred in western Japan. Inheritance or insurance money are possible motives for the deaths, police say.  The widow has inherited nearly $7 million over the past 20 years.

Investigators are treading carefully, however. "Given their advanced age, we have to proceed carefully to judge whether their deaths were actually the result of foul play or not," a police official told AFP.

Kakehi is being questioned by the prosecutor's office,  and denies any involvement in the deaths.

"I absolutely didn't kill (my husband)," she told police. She has not been charged with a crime.