Huawei, the world’s largest telecoms equipment supplier, had earlier accused FedEx of diverting to the US, without any authorisation, two packages that the Chinese company sent from Japan and bound for its offices on the mainland.

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Shenzhen-based Huawei also said FedEx had attempted to divert two more packages to the US that were sent from Vietnam and destined for the Chinese firm’s offices in Hong Kong and Singapore.

Those incidents, which were first reported by Reuters on Tuesday, have prompted Huawei to seek a review of its logistics and document delivery support requirements, according to a Huawei spokesman. The China office of FedEx had earlier denied the incident, saying it was inconsistent with the facts, according to a statement posted on its Sina Weibo account on May 23.

“The recent experiences where important commercial documents sent via FedEx were not delivered to their destination, and instead were either diverted to, or were requested to be diverted to, FedEx in the United States, undermines our confidence,” the Huawei spokesman said. He confirmed all four packages in those incidents had arrived at the FedEx facility in their intended destinations.

Huawei provided images of FedEx tracking records, which showed two packages sent from Tokyo in mid-May and destined for Huawei’s offices, located in Guangzhou and Shanghai, that were diverted by FedEx, without explanation, to the courier’s headquarters in Memphis, Tennessee.

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These tracking records also showed two packages sent from Hanoi on May 17, bound for Huawei’s offices in Hong Kong and Singapore, were returned to sender before FedEx could divert these shipments to the US, according to the Huawei spokesman.

He said Huawei managed to stop the re-routing of those shipments in time, without elaborating on how the company determined that these two other packages were set to be diverted.

An emailed inquiry to the FedEx media relations team did not receive an immediate reply. As such, the authenticity of the FedEx tracking records shown by Huawei could not be verified.

“The shipment is being returned to the shipper,” FedEx said in its post on Sina Weibo. “This event does not represent the high quality delivery services that our customers expect from our more than 450,000 employees worldwide who are committed to provide every day.”

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The issue between Huawei and FedEx has come amid a raging tech war between the world’s two biggest economies, which recently escalated when the US government placed Huawei and its affiliates under a trade blacklist that bars the group from buying hardware, software and services from American hi-tech suppliers without US approval.

A succession of major American technology companies, from Google and Microsoft Corp to Intel and Qualcomm, have suspended their dealings with Huawei to comply with the US trade ban.

US President Donald Trump has also signed an executive order barring US companies from using telecoms equipment made by companies that pose as a threat to national security.