Former Mozambique finance minister, Manuel Chang made a brief court appearance in Johannesburg on Tuesday after being arraigned at the city’s airport over alleged secret loans to Mozambican state companies totalling $2 billion.

Chang sat in the dock as his lawyers argued that his detention on a US extradition request was illegal.

Since his arrest on December 29, three former employees of Credit Suisse bank have also been arrested in London.

Chang, who was finance minister between 2005 and 2015, is accused by US authorities of conspiracy to commit wire fraud, securities fraud and money laundering.

Between 2013 and 2014, Mozambique state-owned security companies borrowed about $2 billion (1.75 billion euros), but the government only disclosed most of the debt to the International Monetary Fund (IMF) in 2016.

The hidden debt plunged Mozambique into its worst financial crisis since independence in 1975.

“Detention of Mr. Chang is illegal because his arrest was effectively on terms of an ineffective warrant,” Willie Vermeulen, Chang’s lawyer, told the court.

Public prosecutor Elivera Dreyer applied for the case to be postponed. Judge Sagra Subroyen agreed, saying she would hand down a ruling on Wednesday.

US prosecutors allege that Chang received $12 million to agree to signing the loan agreements. About $200 million was spent on bribes and kickbacks, according to the US indictment.

Chang, dressed in a dark jacket, dark shirt and jeans, did not speak during Tuesday’s hearing.

Mozambique’s attorney general said Monday there were 18 defendants in their own investigations into the case, but no convictions have been made since the scandal was unearthed in 2015.

In addition to Chang, two other unnamed Mozambican citizens are accused by US prosecutors of being involved in fraud related to the $2 billion debt.

Lebanese businessman Jean Boustani, accused of helping coordinate the alleged fraud, was arrested at a New York airport on January 2.