SEOUL - South Korean prosecutors on Wednesday raided the headquarters of Samsung Group, the country's biggest conglomerate, on bribery allegations involving President Park Geun-hye's longtime confidante Choi Soon-sil.

Choi has been charged with extorting 77.4 billion won (about $70 million) from 53 conglomerates, including Samsung, to set up two non-profit foundations she actually controls.

Samsung made the biggest donations of 20.04 billion won, while wiring 2.8 million euros ($2.9 million) to a German company owned by Choi and providing 1.6 billion won to a sports center for gifted children actually owned by Choi's niece.

The family-run conglomerate is suspected of having donated to receive favors in the merger of the two subsidiaries last July, crucial to the transition of management control to Vice Chairman Lee Jae-yong from his father Chairman Lee Kun-hee who has been hospitalized for two and a half years on heart attack.

The special investigative unit of the Seoul Central District Prosecutors' Office in charge of the Choi case stormed the Samsung headquarters in Gangnam district in the morning, according to local media reports.

The Future Strategy Office, an actual control tower of Samsung Group, was searched, but Vice-Chairman Lee's office was excluded from the search and seizure by prosecutors.

Investigators secured materials on the merger of Samsung C&T and Cheil Industries, which created a de-facto holding company.

Elliott Management, a U.S. hedge fund, opposed the merger due to an unfair exchange ratio of stocks between the two affiliates. Elliott was the third-biggest shareholder of Samsung C&T before the merger.

Despite the unfair ratio, the National Pension Service (NPS) voted for it, enabling Samsung to gain two-thirds of the voting stocks required for the passage at an emergency meeting of shareholders. The NPS was the second-largest owner of Samsung C&T shares at the time.

Prosecutors also raided the headquarters of the national pension fund operator. Local newspaper Hankyoreh reported that the presidential office and then minister of health and welfare pressured the advisory board of the national pension fund into voting in favor of Samsung.

The national fund manager usually hands over sensitive issues to the advisory board, but the vote for Samsung was determined by an internal discussion as over half of the advisors were highly likely to go against the merger.

According to the minutes of the internal discussion secured by Hankyoreh, the NPS officials decided to vote for the merger though they acknowledged that it could cause hundreds of millions of dollars in loss to the national pension fund.

A week after the merger passage, President Park held an open meeting with 17 conglomerate chiefs on July 24, 2015. By the following day, Park met separately one by one with seven heads of them, including Vice Chairman Lee.

Prosecutors are looking into whether Samsung made donations and provided money for the president's decades-long friend in exchange for getting favors in the merger of the two subsidiaries.

If it proves that there was any quid pro quo for the money, President Park and her confidante would face the minimum of 10 years in prison.

Vice Chairman Lee and other senior Samsung executives had been summoned by prosecutors for questioning. South Korean parliament plans to call in Lee as a witness during next month's separate investigation into the scandal involving the president and her friend.