(Bloomberg) -- Tokyo prosecutors may begin questioning lawmakers as soon as Wednesday over a slush fund scandal, the Yomiuri newspaper said, citing a source close to the matter, adding to the turmoil threatening to engulf Prime Minister Fumio Kishida’s administration. 

No one was immediately available to comment at the Tokyo Prosecutors’ Office. The newspaper said prosecutors are looking to launch a full-scale probe following the end of the current session, expected in the late afternoon. 

The premier will give a news conference at 6:15 p.m. where he’s planning to announce he’ll fire four members of his cabinet, the Asahi newspaper said. The ministers and senior Liberal Democratic Party officials are among those accused of concealing income from fundraising events.

The four set to be replaced will include Chief Cabinet Secretary Hirokazu Matsuno, the top government spokesman, as well as trade minister Yasutoshi Nishimura, a key force in Japan’s efforts to revive its semiconductor industry, Kyodo News has reported. All four are members of the once-powerful party faction formerly led by late Prime Minister Shinzo Abe.

Public support for Kishida, already the lowest for a prime minister in more than a decade in some polls, has fallen further on the reports. One LDP lawmaker has already suggested that Kishida could step down as soon as the spring before a party leadership election in September.

Read more: Japan Slush Fund Probe Implicates Premier’s Faction, NHK Says

Kishida has said he plans to take appropriate action in response to the scandal, though he and the politicians said to be involved have declined to comment substantively on the accusations. Kishida has instructed members of his own faction to check whether they had reported income as required. 

Approval for the embattled prime minister tumbled by 6 percentage points from a month earlier to 23% in a survey published by NHK this week, by far the lowest since the LDP returned to government 11 years ago after a period in opposition.

--With assistance from Jon Herskovitz and Takashi Hirokawa.

(Updates with report prosecutors to question lawmakers.)

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