A 35-year-old female bar worker is being investigated in the deaths of five men in Tottori, Japan, police said.

Three of the men had sleep-inducing drugs in their systems and knew the woman, who was not publicly identified, through the bar or as a neighbor, police told Kyodo news in a story published Saturday.

Hideki Maruyama, 57, was found dead in a river in Tottori Oct. 7. Kazumi Yabe, 47, was found dead in the ocean off Tottori April 11 and a third man, in his 50s, was found dead in his condominium late last month after giving the woman his spare key, police said. The third man was not publicly identified.

The two other suspicious deaths involved a man who was run over by a train several years ago and a man who drowned two years ago off the Tottori coast. The two men were acquaintances of the woman, police said.

The woman under investigation was heavily in debt and police were trying to determine if she owed any of the five men money, Kyodo reported.