BEIJING (Reuters) – Chinese authorities in the southern city of Guangzhou detained a U.S. pilot for FedEx Corp (FDX.N) last week on suspicion of smuggling weapons and ammunition after finding suspected air gun pellets in his luggage, the foreign ministry said on Friday.

The man, identified by the Wall Street Journal as former U.S. Air Force pilot Todd Hohn, arrived in Guangzhou having piloted a FedEx freighter aircraft into the city on Sept. 11, Foreign Ministry spokesman Geng Shuang said.

On the morning of Sept. 12, customs at Guangzhou airport found and seized a suspected box of 681 air gun pellets in the luggage of the pilot, Geng said, adding he had been due to fly to Hong Kong that day.

He was later released from custody, subject to provision of a surety, pending investigation for the suspected smuggling of weapons and ammunition, Geng told a daily news briefing.

The Journal said Hohn was not being allowed to leave China until the investigation concludes.

Hohn could not be reached for a comment, and calls to the Guangzhou police were not answered.

FedEx, which did not name Hohn, said in a statement it was “working with the appropriate authorities to gain a better understanding of the facts.”

A FedEx spokeswoman declined to give any details when asked if Hohn was being prevented from leaving China.

Hohn’s detention comes at a difficult time in China for FedEx, which has become one of the most high-profile corporate brands to get caught up in the U.S.-China trade dispute and other frictions.

The Memphis-based company has been the target of Chinese ire over shipping mistakes involving several packages, including parcels addressed to China’s Huawei Technologies Co HWT.UL, which Washington has put on an export blacklist.

Geng did not name Hohn, but said Guangzhou customs had blocked the pilot from leaving the country “on suspicion of smuggling weapons and ammunition.”

Chinese authorities informed the U.S. consulate in Guangzhou a day after he was detained, Geng said, adding that the case was still under investigation.

A U.S. State Department official said the department was tracking developments.

“We take seriously our responsibility to assist U.S. citizens abroad, and are monitoring the situation,” the official said in an email to Reuters.

The Wall Street Journal first reported the case on Thursday.

Earlier this week, FedEx slashed its fiscal 2020 profit forecast by 18 percent. Executives said the U.S.-China trade war is dampening key economies in Europe and Asia and hurting its Express business, which moves parcels and freight via airplane around the globe.

Hong Kong, where the Journal said Hohn lived, has been rocked since June by large, sometimes violent street protests that have presented Beijing with its biggest political challenge in decades.

Reporting by Ben Blanchard in Beijing, Rachit Vats in Bengaluru and John Ruwitch and Brenda Goh in Shanghai; Editing by Shinjini Ganguli, Cynthia Osterman, Tom Hogue & Kim Coghill