South Africa's government is investigating if the Indian embassy abused diplomatic privileges over a society wedding, an official has said.
The embassy is alleged to have helped a wealthy Indian family gain landing rights for a private jet at a military base near the capital, Pretoria.
The Gupta family flew guests, reportedly including Bollywood stars and Indian government officials, to South Africa for the wedding.
The family denies any wrongdoing.
The Gupta brothers - Atul, Ajay and Rajesh - are said have wielded enormous influence in South Africa since white minority rule ended in 1994.
Their business interests cover mining, aviation, technology and the media.
Two of President Jacob Zuma's children have served as directors of Gupta-owned firms, according to South Africa's companies database, the AFP news agency reports.
On Wednesday, the governing African National Congress (ANC) party and the Congress of South African Trade Unions (Cosatu) demanded an investigation into how the guests of the family flew from India to the Waterkloof Air Force Base near Pretoria.
"The African National Congress, driven by the concern for the safety and sovereignty of South Africa, shall never allow a situation where our ports of entry and National Key Points are penetrated with impunity," ANC Secretary General Gwede Mantashe said in a statement.
Police escorted the guests to the casino resort of Sun City for the wedding of 23-year-old Vega Gupta, the Gupta brothers' niece, to Indian-born Aaskash Jahajgarhia.
On Thursday, Minister in the Presidency Collins Chabane said top-level investigations were under way to establish how the chartered flight landed at the military base.
The investigation would also unearth whether diplomatic privilege had been abused, he added.
"The investigations will point out to us if that is the case," Mr Chabane is quoted by Bloomberg news agency as saying.
"If so, the necessary steps will be taken. This is a serious matter."
Gupta family spokesman Haranath Ghosh said South African officials had authorised the landing of the plane following a request by the Indian embassy in Pretoria.
"Waterkloof Air Force base was used with full permission of the authorities to receive foreign dignitaries, including some ministers," Mr Ghosh said, Bloomberg reports.
South Africa's International Relations Department said the Chief of State Protocol, Bruce Koloane, had been placed on suspension while an investigation took place.
The Indian embassy has not yet commented on the affair.