Mayumi Saito, 53, was arrested Tuesday on charges of abandoning bodies, a day after she turned herself in at an Osaka police station.
Police said human bones were identified in buckets found in Saito's apartment.
The police official requested anonymity due to department policy.
Saito was quoted by police as saying she put the bodies into concrete from 1992 through 1997 because she had been too poor to raise them, but she had been filled with guilt.
Saito had a part-time job, but details of her work and family were not available.
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