A 42-year-old mathematics teacher in custody over a Tokyo high school bombing in March was served a new warrant Monday in connection with the bombing of a metropolitan government education official's home, officials said.

Kotaro Matsumura, a math teacher at Tokyo Metropolitan Hiroo High School, was arrested March 12 after he planted a homemade bomb in the principal's desk at the nearby Tokyo Metropolitan Mita High School. He was charged with attempted murder in the case, although nobody was hurt when the bomb exploded.

Matsumura has since admitted during police interrogations that he planted a bomb at the home of Tomohisa Narukawa, deputy director general of the metro government's Office of Education in Ichikawa, Chiba Prefecture, in February.

Police had determined that the bomb in the Mita incident was similar in structure to the one used in the bombing of Narukawa's house, the officials said.

According to the officials, Matsumura set the homemade bomb, which was in a metal box, at the gate of Narukawa's house early on the morning of Feb. 9.

The bomb exploded when Narukawa's 25-year-old daughter opened the gate at 6:38 a.m. She suffered an ankle wound that required three weeks of treatment.

Matsumura has told investigators he bore a grudge against Tokyo's education authorities because he thought they were tightening control over teachers at public high schools.

He was also angered that he had not been given a special pay raise at the Hiroo school. Such pay raises are distributed to teachers at the principal's discretion.