TOKYO, June 9 (Xinhua) -- Japan's Education Minister Hirokazu Matsuno said Friday his ministry will reinvestigate the existence of documents central to an ongoing scandal possibly implicating Prime Minister Shinzo Abe and the government in providing a close friend of Abe's with favorable treatment to open a new school.

Matsuno told a press conference on the matter that an initial probe by the ministry had been deemed insubstantial and the public is calling for a more comprehensive probe to be launched.

"We sincerely accept the people's voice and will conduct an additional investigation over the internal documents," Matsuno said.

The documents, according to the opposition camp, could prove that the prime minister used his position to influence the government's approval for Kake Educational Institution, run by a close friend of Abe's, to open a new veterinary school at a location highly deregulated by the government.

Matsuno said that the prime minister himself had called for the fresh probe to be launched and to be conducted quickly and thoroughly.

The original probe launched by Matsuno lasted just two days and it was concluded that the potentially damaging documents' existence could not be confirmed.

A former vice education minister at the beginning of the month, however, released a statement backing up his previous assertions that senior government advisors had pressurized him to accelerate procedures to open up a new school with close links to Abe.

Kihei Maekawa said in a statement that last year in August, Isao Kiso, an advisor to the Cabinet at the time, visited his office and requested that he accelerate procedures for the opening of a new veterinary school.

Okayama University of Science was handpicked by the government to open the new veterinary medicine school, in Ehime Prefecture, one of Japan's national strategic special economic zones, which has far more relaxed regulations to boost growth in the area, as part of Abe's overall growth strategy.

Kake Educational Institution, which operates the university and, controversially, is chaired by Abe's close friend, was selected for the project in a meeting held between the central and local governments in the special strategic zone in January.

The local city assembly provided the land to the institution to build the new department for free and in addition they provided 9.6 billion yen (86.24 million U.S. dollars) as a subsidy for the school's construction costs.

Maekawa stated that Kiso asked him to speed up the procedures for opening the veterinary school and that it was his understanding that Kiso was specifically referring to the government's plan involving Kake Educational Institution, because he was a senior official of the institution at that time.

Maekawa also said that Kiso told him that his ministry need to do nothing except follow the decision made by the Council on National Strategic Special Zones, which is chaired by Abe.

The former vice education minister has offered to give testimony in parliament over the scandal.

He also said he met Hiroto Izumi, an assistant to Abe, at the prime minister's office, when the selection of the strategic zone was underway and was also pressurized to speed up procedures for the new school at that time.

The government so far has refused to summon Maekawa or Izumi to give testimony in parliament as sworn witnesses, despite the opposition camp vociferously calling for it to do so.

It also came to light recently that Abe had been on Kake's payroll and had received a salary apparently for duties carried out there for a couple of years after he was first elected to the House of Representatives in 1993.

Abe, when quizzed on his financial connections to the institution, said it was a long time ago and that he was fuzzy on the details.

Along with Maekawa, the opposition camp believe that an education ministry advisory panel was currently assessing an application to open the new veterinary school and the ministry had prepared a document stating that the Cabinet Office said that "Abe backs the plan."

The document also reportedly suggests that the education ministry was told by the Cabinet Office that the choice for the new department "was heard to have been the prime minister's wish."

The main opposition Democratic Party also maintains that one of the documents in question shows that negotiations had taken place between the ministry and the Cabinet Office regarding the set timeframe for opening the new department at the university.

As for the timing for opening of the new department, which was scheduled for April 2018, one document reportedly states, "This is what the highest level of the prime minister's office has said."

Another document mentioned that opening the department at an early juncture was "in line with the prime minister's wishes."