Abe and his finance minister Taro Aso face mounting pressure over the scandal, which has resurfaced in recent days with allegations that officials altered key evidence to parliament.
The scandal emerged last year and concerns the sale of land to a close friend of Abe at a price said to be around one tenth of its normal value.
Opposition politicians have alleged the buyer of the land -- a right-wing operator of private schools -- was able to clinch the sale at such a favourable price because of his ties to the Abe family.
The original documents included the names of several politicians, which were deleted before being submitted to lawmakers, mass circulation Yomiuri Shimbun and other media reported today.
More From This Section
The Mainichi Shimbun has reported the documents were doctored to be "coherent" with a speech made in parliament by the head of the tax agency Nobuhisa Sagawa, who stepped down on Friday over the scandal.
"It is possible that Sagawa ordered the alterations," the newspaper said, citing government sources.
Adding to the pressure, a finance ministry official linked to the scandal was found dead on Friday, although it is not clear if the reported suicide is linked to the affair.
Abe has consistently denied any wrongdoing and vowed to resign if he was found to be involved in the land deal.
But a poll released published today in the Yomiuri Shimbun showed his support dropping by six percentage points from last month to 48 per cent, the first reading under 50 per cent since winning re-election in October.
The allegations have also paralysed parliament in recent days, with some opposition lawmakers boycotting debates.