Officials at Samsung Group and National Pension Service confirmed investigators visited their offices in Seoul. The Investment Management Office of the world's third-largest pension fund was the target of the raid, according to an NPS official who declined to be named, citing office rules.
Samsung spokeswoman Lim Bomi declined to say which Samsung department was raided.
Prosecutors at the Seoul Central District Prosecutors' Office did not return calls seeking comment.
Also Wednesday, South Korea's presidential office said the justice minister and senior presidential secretary for civil affairs had offered to resign. The president has not accepted their resignation offers, it said.
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While Park faces mounting calls to resign over the scandal, public anger has also been simmering toward Samsung as well because of its alleged links with Choi.
South Korea's Yonhap news agency reported earlier that prosecutors were looking into whether the presidential office played a role in the pension service's vote to support the controversial merger of two Samsung companies last year.
Samsung narrowly won shareholders' approval to merge Samsung C&T and Cheil Industries in July 2015.
Most investors and analysts questioned Samsung's argument that the deal was to create synergies between a Samsung construction firm and another Samsung firm that ran an amusement park and fashion businesses.
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