Communist China’s efforts to weaken the Hong Kong protest movement include blocking the shipment of the black clothing, masks, and umbrellas favored by protesters.

Reuters on Friday was told by representatives of China’s major courier services that bans were put in place on the shipment of multiple black clothing items to Hong Kong customers, beginning in August. They said any shipment with more than five such items has been blocked.

The couriers also said they have been forbidden to shop “any items that can be used by mobs,” including masks and bulk orders of umbrellas or sticks.

According to Reuters’ follow-up reporting, importers in Hong Kong appeared to be unaware of these restrictions, while retailers reported sales of black clothing remain brisk. Several Chinese courier firms declined to comment when asked about the rules.

The South China Morning Post on Thursday said it obtained a July 11 notice from a Chinese courier company called PHXBUY, based in Guangdong, that said customs officials had ordered a halt of deliveries that “include yellow helmets, yellow umbrellas, flags, flagpoles, poster banners, gloves, masks, black T-shirts, metal rods, fluorescent tubes, and bludgeon clubs.”

“We cannot take delivery of the above products,” PHXBUY informed its clients.

On September 26, another Guangdong shipping company called EXPRESS sent its customers an even longer list of items that could not be shipped:

Foodstuffs, liquid, powder, gases, counterfeit brand products, big machines, helmets, umbrellas, wrist bands, towels, safety vests, speakers, amplifiers, trestles, walkie-talkies, drones, black shirts and other clothing, goggles, metal beads, metal balls, horticulture scissors, metal chains, torches, binoculars, and remote-controlled toys.

EXPRESS warned clients that any unauthorized shipment of the banned goods would be subjected to a “thorough investigation,” and said all shipments must include the correct names of those mailing the items plus an accurate list of everything being sent.

The SCMP contacted another courier and was told shipments of black clothing have been banned, and found at least one online retailer who said orders of black clothes sent to Hong Kong are not getting through.

The UK Daily Mail on Thursday reported “a batch of black clothing from a U.S. sportswear brand was recently intercepted by Chinese officials when it was being transported from its factory in Shenzhen to Taiwan,” suggesting the ban on black is spreading beyond Hong Kong.

The U.S. brand in question does not yet appear to have complained in public about the seizure of its goods. The Daily Mail described it as “a famous brand being sold in 45 countries.”