The transport ministry filed a criminal complaint Monday against Hokkaido Railway Co. over alleged falsifications of maintenance data, prompting the police to open a criminal investigation into the matter.

The move by the Land, Infrastructure, Transport and Tourism Ministry marks the first criminal case brought against a railway for an alleged violation of the Railway Business Act, which can result in a fine of up to ¥1 million.

The Japan Transport Safety Board, which handles accident investigations, followed the move by accusing JR Hokkaido of breaking the Act for Establishment of the Japan Transport Safety Board, which sets the rules of conduct for the JTSB.

The Hokkaido Prefectural Police accepted the two complaints and launched an investigation team with 160 officers. They will search the railways' head offices in Sapporo this week, investigative sources said.

"The maintenance data falsifications and destruction of facilities are extremely malicious," Chief Cabinet Secretary Yoshihide Suga said at a press briefing. "I hope JR Hokkaido will make a full effort to rebuild public trust as early as possible."

JR Hokkaido is suspected of faking rail width data immediately after a September 2013 derailment occurred on the Hakodate Line, and on the day before a special ministry audit, according to the transport ministry.

The complaints do not identify any individuals involved in the alleged acts, but JR Hokkaido earlier fired five staffers regarding their involvement in data falsifications that were linked to the derailment.

JR Hokkaido's internal investigations have found that 129 members of a 795-member workforce maintenance team had taken part in falsifying data, and that falsifications were observed in 33 of its 44 railway maintenance sections.