TOKYO, May 21 (Xinhua) -- A new document revealed on Monday showed Japanese Prime Minister Shinzo Abe may have known of a scandal-hit school project two years earlier than he previously admitted, casting doubt over the credibility of the premier's previous explanations.

Abe has been accused of using his influence to facilitate a government decision to approve the heavily-subsidized opening of a veterinary school at an university run by his friend Kotaro Kake.

The new document, submitted by the Ehime prefectural government to the Diet on Monday, showed that Kake told Abe about his intention to provide veterinary education meeting international standards during a meeting on Feb. 25, 2015.

The prime minister, however, previously said that he learned of the project on Jan. 20, 2017, when a government economic panel approved the project.

The veterinary school, which opened last month in western Japan is located in a specially deregulated zone in Ehime prefecture.

Abe has close ties with the school's operator, Kotaro Kake, and suspicions have long been circling that Abe used his influence in the government's approval of the newly-opened department at the Okayama University of Science.

Abe has repeatedly denied the allegation but support rate for his cabinet has once declined sharply over this and a number of other scandals implicating him and some of his cabinet members.

The surfacing of the Ehime document followed another one found last month which stated that Tadao Yanase, former secretary of Abe, informed local officials that the veterinary school project is a "matter concerning the prime minister" during a meeting at the prime minister's office on April 2, 2015.

Yanase, who is now vice minister for international affairs at the Ministry of Economy, Trade and Industry, has denied making the comment, adding that he does not remember such a meeting with the local officials.

The surfacing of the alleged documents threatens to put Abe and his administration on even shakier ground.

Yuichiro Tamaki, co-head of the new Democratic Party for the People, said that the prime minister's cabinet should resign en masse.

Akira Koike, head of the secretariat of the opposition Japanese Communist Party, called for further investigations over the issue.