USAID said on Wednesday that it has suspended a number of humanitarian aid activities acting out of Turkey, as well as barring a number of individuals and vendors from receiving US funds.

The move follows an investigation by USAID’s Office of Inspector General after concerns were raised by an organisation implementing the agency’s work.

In a statement last week, the USAID OIG said: “The investigation to date has identified a network of commercial vendors, NGO employees and others who have colluded to engage in bid-rigging and multiple bribery and kickback schemes related to contracts to deliver humanitarian aid in Syria.”

Two major aid agencies – the International Rescue Committee, headed by former UK foreign secretary David Miliband, and the International Medical Corps, which is one of the largest suppliers of medical aid to Syrians – have been implicated.

Both are among “several NGOs delivering aid to Syria” that have terminated staff members as a result.

The IRC has reportedly fired two staff members for taking bribes while the IMC has laid off 800 employees and fired three suspected of being involved.

A spokesperson for USAID told the Thomson Reuters Foundation that neither the IRC nor the IMC has been suspended from USAID funding, despite reports in other media that they have.

The IRC in particular relies heavily on financial support from the US and British governments.

USAID said it is working to reduce the impact of the suspension on the flow of humanitarian aid to those in need in Syria.

It added: “USAID places the highest priority on ensuring that taxpayer funds are used wisely, effectively and for their intended purpose.

“We have a zero tolerance policy for fraud and abuse of American taxpayer resources and will take every measure at our disposal to recover misspent funds.”