Chinese authorities sent an inquiry letter to US courier service FedEx on Friday for its alleged misconduct in misrouting Huawei documents to the US, signaling the official launch of the probe on this matter, the Xinhua News Agency reported on Friday. 

The investigation follows an incident that FedEx had diverted two parcels of Huawei destined for an address in China to the US, and two others from Vietnam to Hong Kong and Singapore, respectively, were also diverted to a US address.

The US firm apologized for the incident, which, however, failed to impress public opinion in China due to the absence of a detailed explanation.

Although FedEx has denied widespread speculation in China that the US courier service was working with the Trump administration to interrupt Huawei's normal business activities, Chinese experts said that to regain public trust, the US firm must provide a more detailed and responsible explanation.

Washington has launched a clampdown on Huawei for so-called security risks in Huawei's equipment.

"By investigating whether FedEx sent the parcels deliberately or by accident, the Chinese government is giving a second chance to foreign firms which make mistakes to appeal," Bai Ming, deputy director of the Ministry of Commerce's International Market Research Institute, told the Global Times on Friday. 

This is in sharp contrast to the brutal US crackdown on Huawei, which cited national security but never showed solid evidence, analysts said. "Chinese regulators' decision on FedEx is responsible and professional," Bai said.

Industry insiders said the investigation cannot be completed once and will be conducted multiple times in order to figure things out. But whatever the results are, it will take a toll on the courier's business. 

"If the investigations show that FedEx received orders from the Trump administration, then the US firm will be immediately put into the unreliable entity list," Huo Jianguo, vice chairman of the China Society for World Trade Organization Studies, told the Global Times.

China's Ministry of Commerce announced last month that it will soon release an "unreliable entity list" targeting foreign firms that seriously undermine the legitimate interests of Chinese companies.

"Even if the results prove FedEx sent the parcels by accident, that also shows the firm's system has some technical issues, which will hurt its global reputation," Huo added. 

FedEx said in an earlier statement that it will fully cooperate with investigations, saying it attaches great importance to Chinese customers.