A woman was arrested Wednesday in Hiratsuka, Kanagawa Prefecture, for allegedly killing her daughter after five bodies were discovered in an apartment earlier this week.
Chizuko Okamoto, 54, was arrested on suspicion of strangling her 19-year-old daughter, Rikako, police spokesman Motoyasu Ito said.
The bodies of the daughter, her 35-year-old husband and their three infants were found in their apartment Monday by the husband's mother, according to Ito.
The man was found hanged to death, but it was not immediately clear how the children had died, he said.
Chizuko Okamoto told police she had lived in the apartment until March, according to NHK TV.
Police initially believed the parents killed their children and then committed suicide, but evidence was later found suggesting the woman had been murdered, Ito said.