Chinese authorities have raided the office of a US firm in Beijing, shutting down its operations and detaining five Chinese staff, the company has said. Mintz Group, which has offices in 18 cities around the world and offers corporate analysis and due diligence services, said it received no legal notice about the reasons for the unannounced raid. “We can confirm that Chinese authorities have detained the five staff in Mintz Group’s Beijing office, all of them Chinese nationals, and have closed our operations there,” the company said in a statement on Friday, according to Reuters. “Mintz Group received no advance…