(Adds Sanlam statement)
JOHANNESBURG, Dec 21 (Reuters) - South African investor Christo Wiese has sold an additional 1.1 billion rand ($87 million) of shares in supermarket group Shoprite, exchange filings showed on Thursday, after his exposure to scandal-hit retailer Steinhoff dented his fortune.
More than $14 billion of shareholder value has been wiped off Steinhoff over the last three weeks after the owner of Mattress Firm and Conforama discovered what it called accounting irregularities and parted company with its chief executive.
The 90 percent collapse hit Wiese's wealth -- estimated by Forbes magazine to have dropped to below $1 billion -- the hardest as he is the largest Steinhoff shareholder with a stake of about 20 percent.
Exchange filings showed Wiese sold 5 million shares at an average price of 221.5 rand each in Shoprite, a 128 billion rand ($10.1 billion) company in which he owns about 17 percent stake and is chairman.
That brings the money he has raised since Dec. 14 from the sale of Shoprite stock to 3.3 billion rand ($260 million). It is unclear what he would be using the money for and his office did not immediately respond to a request for comment.
Wiese borrowed 1.6 billion euros ($1.9 billion) to buy additional Steinhoff shares in September 2016, pledging 3.2 billion euros of his existing holding as security to the investment banks that lent the money.
Shares in Steinhoff dropped a further 11 percent on Thursday, extending the decline to the second day after the company said some lenders have started restricting access to credit lines.
Wiese was one of the early directors of a budget retailer Pepkor, which was co-founded by his parents in 1960 in Upington on the southern edges of the Kalahari desert.
He is best known for transforming Shoprite from just six shops in the 1970s to hundreds of stores across Africa.
Separately, financial services firm Sanlam Group, which has exposure to Steinhoff's debt and equity instruments, said the potential impact on the group's 2017 and future earnings was not significant.
Sanlam said the decline in the value of Steinhoff shares held in its capital portfolios was to a large extent protected by equity hedges in place.
Sanlam is the second firm to disclose Steinhoff's impact on its investments after Anglo-South African investment bank and asset manager Investec,. ($1 = 12.7004 rand) ($1 = 12.7004 rand) (Reporting by Tiisetso Motsoeneng, additional reporting by Nqobile Dludla; Editing by Keith Weir)