A second arrest warrant was served on a 17-year-old boy Monday over the theft of some 210,000 digital files containing the grades of students in Saga Prefecture schools, police said.

The boy, a resident of the city of Saga, is suspected of accessing an online system used by the prefecture's public junior high and high schools. The boy saved files containing personal information, including home addresses, to his personal computer, police in Tokyo said.

The boy, who has not been named because he is a minor, has allegedly admitted to the charges.

According to the police, he had formed a group with several other youths ranging in age from 16 to 18, and was boasting of his success at stealing IDs and passwords by uploading them onto a website.

The boy was first arrested June 6 for allegedly creating an unlawful program to gain access to paid TV programs, which were then made available for online distribution.

The latest charges are for unauthorized access to the school system from Jan. 16 to 18 and to another online system of a prefectural high school on Jan. 20.

In relation to the case, the police have referred a 16-year-old male high school student in Saga to prosecutors, suspecting him of also making unauthorized access to the same high school's system.

This teen, who was among the group that included the 17-year-old, allegedly said the boy provided the information he needed to access the system.

The Saga Education Information-Network, introduced in 2014, covers some 210 schools and allows teachers to manage grades, class attendance and other student information on a server, while enabling students to download educational materials and take tests online using IDs and passwords.