The computer engineer at the center of the big data scandal at Benesse Corp. was served a fresh arrest warrant Monday on suspicion of stealing data on about 20 million of its customers, Tokyo police said.

Masaomi Matsuzaki, 39, who was hired as a systems engineer by Synform Co., an Okayama-based affiliate of Benesse Holdings Inc., Benesse's parent, allegedly copied the data onto a memory card in his smartphone from Synform's office in Tama, western Tokyo, on June 27.

The fresh warrant for breaking the unfair competition prevention law follows Matsuzaki's indictment last Thursday over a separate theft of data linked to 10 million customers of the major correspondence education provider for children.

Japan's biggest data theft scandal has prompted calls to revise the law on personal information protection.

Matsuzaki was arrested July 17 for allegedly copying the 10 million customers' data on June 17. The data were sold to name-list traders and might have been resold to a few hundred companies, investigative sources said last week. He told the police he sold the data to three name-list traders for ¥4 million, the Tokyo police said.

One trader who purchased the data told the police it was resold to about 50 firms, including cram schools, kimono shops and photo studios, investigative sources said.

But he may have had problems selling the second batch allegedly stolen on June 27, which included the names, telephone numbers and birth dates of 20 million customers, as Benesse launched its internal investigation that day after customer inquiries spiked about a potential privacy breach, investigative sources and other people close to the matter said.