The collapse of a concrete block wall which killed a 9-year-old girl in quake-hit Osaka may have resulted from a lack of required safety inspections in recent years, a senior local education board official said Friday.

"We cannot deny the possibility that (her death) was a man-made tragedy," Toru Hirano of the Takatsuki education board said at a press conference.

The magnitude-6.1 quake which rocked western Japan on Monday registered lower 6 on the Japanese seismic intensity scale of 7, leaving five people dead in Osaka Prefecture and over 400 injured in seven prefectures.

The education board said a safety check on the concrete block wall at Juei Elementary School in Takatsuki was required every three years, but the wall had not been inspected thoroughly in recent years.

Education board officials without any architectural qualification assessed the structure by hitting it with a stick in 2016 and reported to the school that there was no safety problem. An inspection was not carried out three years before that, the education board said.

Rina Miyake was crushed to death as the wall collapsed on her when the quake hit Monday morning.

School authorities were warned three years ago about the substandard concrete wall that collapsed onto the girl, the education board said.

(Flowers are placed at the entrance gate of Juei Elementary School)

Disaster prevention adviser Ryoichi Yoshida informed the girl's school and the local education board in 2015 about the danger of the wall made from concrete blocks piled up high around the swimming pool of the school.

Inspections have found 15 elementary and junior high schools in Takatsuki had concrete block walls that may not meet safety requirements of the law, according to the board.

A total of 59 city-run schools were inspected, and concrete walls at 11 schools were found to have been built on a similar manner to that of Juei Elementary School, according to the board.

The walls in question at 15 schools -- nine elementary schools and six junior high schools -- are expected to be removed within two to three weeks, the education board said.

The inspections were conducted on Tuesday at 41 elementary schools and 18 junior high schools.

In addition to Takatsuki, similar block walls have been found at a number of schools in other parts of Osaka, Kyoto and Hyogo prefectures. In Saitama Prefecture near Tokyo, about 350 schools have similar walls which may have structural flaws.

Land minister Keiichi Ishii, who visited Osaka to inspect the quake damage, told reporters that the ministry will consider providing financial support for removal or repair of cinder block walls at companies and residences.

While apologizing for its failure to prevent the tragedy at the elementary school, the board said it did not view the wall as being in violation of the law and considered it posed no problem as there were no cracks.

But Yoshida has told Kyodo News that concrete experts should have assessed the wall's safety and expressed skepticism about the board's handling of the matter.

Yoshida, who gives anti-disaster lectures across Japan, gave a speech on disaster prevention at the elementary school on Nov. 2, 2015, after assessing dangerous points on routes taken by pupils going to school by walking along such roads himself. He told the school's vice principal at the time about the potential risk of the concrete wall.

To remind the school about the danger, he sent an email to the school on Dec. 7 the same year and attached data to back up his claim. He warned the school that concrete walls built before the 1981 revision to the building standards law need particular attention.

The board said Yoshida's advice was not shared within the organization.

Education minister Yoshimasa Hayashi said Friday in a news conference, "If safety measures were not taken despite warnings, we need to thoroughly verify (the response)."

The wall, reaching as high as about 3.5 meters including its 1.9-meter foundation, was made of blocks piled up higher than legal standards with insufficient reinforcement.

Local police are looking at her death as a possible case of professional negligence.

A total of 3,416 residential structures in four prefectures -- Kyoto, Osaka, Hyogo, and Nara -- were damaged in the disaster, according to the Fire and Disaster Management Agency.

In Osaka Prefecture, 499 people were still taking shelter at evacuation centers as of Friday afternoon.