South Africa's currency has weakened amid a public dispute between the country's finance minister and police investigators.

Markets opened Wednesday with the South African currency at 16 rand to $1, a low not seen since December when the country shuffled three finance ministers in one week.

The police's Directorate for Priority Crime Investigation unit said in a statement that Minister Pravin Gordhan failed to cooperate with an investigation into the South African Revenue Service.

According to a statement by Gordhan, the police unit sent him a list of questions, setting the deadline for his response within days of the minister's annual budget speech and again when Gordhan was traveling to restore investor confidence in South Africa.

The dispute comes as ratings agencies consider downgrading South Africa's credit rating.