KYOTO - A woman indicted over the death of one daughter and injury to another was arrested Thursday on suspicion of causing the death of yet another daughter in 2004 by contaminating her intravenous drip, according to police.

Police said Kaori Takagi, 36, admitted injecting tap water into the girl's IV, but claimed she had no idea what killed her.

According to a joint force of the Kyoto and Gifu prefectural police, which arrested Takagi, she injected tap water into the IV of 2-year-old Yui Takagi on multiple occasions from July to August 2004 at Gifu University Hospital in Gifu.

The girl died in October of that year.

The girl had been hospitalized since June because she had been running a fever. The official cause of death was listed as a fungal infection of the lungs.

Prior to Thursday's arrest, Takagi had been arrested on suspicion of murdering her fourth daughter, then 8 months old, and attempting to murder her 2-year-old fifth daughter.

Psychiatric tests concluded she was criminally responsible for the deeds.