The file photo shows police officials stand in front of the fence outside the Union Buildings, the official seat of the South African government, in Pretoria, on Oct. 20, 2016. (Xinhua/Zhai Jianlan)

CAPE TOWN, March 9 (Xinhua) -- South Africa's opposition party has called for an independent investigation into suspected involvement of corrupt cops in an airport heist of a large amount of cash.

This came after an astounding 24 million rand (about 1.9 million U.S. dollars) in cash was reportedly stolen from a South African Airways plane at the OR Tambo International Airport in Johannesburg.

A group of armed suspects posing as police in a marked police vehicle allegedly intercepted security guards as they were transporting money to a waiting aircraft. No shots were fired and no injuries have been reported.

"The use of a police vehicle in this incident is extremely concerning and could point to the involvement of corrupt cops," the Democratic Alliance (DA) said in a statement on Wednesday.

The DA said it will write to the Independent Police Investigative Directorate (IPID) to request that it conduct a thorough investigation into whether or not South African Police Services (SAPS) members or assets were involved in the heist.

The DA will also submit parliamentary questions to find out how many SAPS vehicles and firearms have been found to have been used for criminal activity, as well as how many SAPS members have been found guilty of criminal offences, DA Shadow Minister of Police Zakhele Mbhele said in Cape Town.

Furthermore, the DA will also be submitting questions to the Ministers of Police and Transport to determine the state of security at the country's airports, said Mbhele.

"The SAPS should be protecting the lives and property of South Africa's people and we should not be seeing the use of official resources by corrupt cops to enrich themselves," Mbhele said.

Meanwhile, the Airports Company South Africa (ACSA) said it is working closely with law enforcement agencies to arrest those behind the armed robbery.

"South African Police Service and Airports Company South Africa is working closely with other law enforcement agencies to apprehend the suspects. The investigation is at an early stage," the ACSA said.

The SAPS said involvement of corrupt cops could not be ruled out.

The boldness of the criminals as well as their ability to gain access to a secure area highlights the severity of crime in South Africa.

It is not the first time that large amount of cash was stolen at Johannesburg's central airport.

In 2006, an estimated 7.67 million dollars were stolen from an international aircraft at the same airport.