Jung Hyun-sik, a former secretary general of the K-Sports Foundation, told local media that An had instructed him to demand 8 billion won from SK Group.

According to data from Chaebul.com, a total of 53 corporations had donated a combined 77.4 billion won to the foundations. Hyundai Motor led the group with 6.88 billion won, followed by SK Hynix and Samsung Electronics with 6.8 billion won and 6 billion won, respectively.

But 12 companies had made contributions while reporting losses, fueling suspicions that they were pressured to make the donations.

The prosecution has already raided An’s home and his office in Cheong Wa Dae to look for evidence concerning the allegations.

The prosecution has stepped up its investigation into the Choi scandal, visiting eight banks with a search warrant as of Tuesday to investigate the financial transactions of those with links to the scandal.

In a bid to acquire financial transaction records of those related to the allegations, investigators visited headquarters of eight banks -- Woori Bank, Standard Chartered Bank Korea, Shinhan Bank, KB Bank, KEB Hana Bank, Industrial Bank of Korea, Citibank Korea and Nonghyup Bank -- to collect relevant documents.

The data requested by the prosecution includes those related to Choi and TV commercial director Cha Eun-taek, who is suspected to have played a role in founding the two aforementioned entities and interfering in several state-backed culture projects.

The sweeping search indicates that the investigators have commenced a comprehensive crackdown on the financial records of those related to the scandal.

Among the banks searched, KEB Hana Bank is suspected of granting Choi’s daughter Chung Yoo-ra loans under unlawfully favorable conditions.

Rep. Jung Jae-ho of the minor opposition Minjoo Party of Korea has alleged that Chung and Choi had been granted a loan of 250,000 euros ($274,225) last year, which they supposedly used to buy real estate in Germany.

The Financial Supervisory Service is conducting investigation into the allegation, and National Tax Service chief Lim Hwang-soo told Parliament on Monday that the NTS is investigating possible tax evasions by Choi and Chung.

Prosecutors are also investigating a claim that Choi was allowed to freely enter and leave Cheong Wa Dae.

Local daily the Hankyoreh, citing officials from the presidential office, reported that Choi had frequently visited Cheong Wa Dae from 2013 until recently without going through inspection or identification process. The gate that Choi used was reportedly one used exclusively by Cabinet members, who go through identification.

Park’s former Chief of Staff Lee Wong-jong had said that it was not true “as far as I know.”

The prosecution has questioned Choi’s associate Ko Yeong-tae and former Cheong Wa Dae staff on the allegation, including Park’s personal trainer Yoon Jeon-choo, officials said Tuesday.

It has been rumored that Yoon was able to work in the presidential office on Choi’s recommendation.

When asked about the allegation, Cheong Wa Dae spokesman Jung Youn-kuk said that the presidential staff would cooperate with the investigators “the best they can.”

The presidential office Sunday refused to cooperate when prosecutors attempted to execute a warrant to search Cheong Wa Dae, citing reasons of national security. Instead, Cheong Wa Dae staff voluntarily submitted what they said were relevant documents.

By Yoon Min-sik (minsikyoon@heraldcorp.com)