Recyclables were also spotted dumped outside other closed collection points and green groups said they feared the problem could get worse after the introduction of a waste charging scheme next April.

A department spokeswoman on Tuesday said that although all stations were closed for two days over Christmas, self-help collection boxes or cages had been put outside the storefronts and operators had been told to clear full containers as soon as possible.

“The department will issue a warning letter to the operating organisation regarding the incident, requesting it to step up monitoring and clean up recycling materials outside the shop in a timely manner to prevent similar incidents from happening again,” she said.

The department added later it would become mandatory for all recycling operators to provide additional recyclables collection over holiday periods and to set up CCTV cameras to monitor their premises.

Officials also reminded the public to avoid leaving recyclable material outside the stations.

Staff at the centre on Tuesday cleared the front of the station and dealt with the backlog.

“It was so outrageous when I spotted it, so I uploaded the photo to the group,” said one of the Facebook posters, a Hung Hom resident who gave his name only as Wong.

Wong wrote in his social media post that “the quality of Hung Hom residents is so embarrassing”.

A waitress in her early 20s, who works opposite the recycling centre and identified herself as Nancy, said the scene was “quite shocking”.

“With the rubbish piling up, it made the neighbourhood look bad,” she said.

She added that the pile of waste should have been cleared, even if the centre was closed over the holiday.

A woman named Fong, working in a nearby shop, said the pile had reached the top of the centre’s front door.

Free reusable food container vending machines set up at Hong Kong universities

“Of course it does not look good, but I do not think the neighbours would complain, as the pile did not affect pedestrians,” she said.

Bags of recyclables, although in smaller quantities, were also seen outside other recycling stores in the city’s government-funded Green@Community network, administered by the Environmental Protection Department.

The Hung Hom operation, opened in July and operated by NGO the Christian Family Service Centre, is one of 44 Green@Community recycling stations and stores.

There are also more than 100 mobile collection booths around the city.

A representative of the under-fire Hung Hom operation declined to comment until it had further talks with authorities.

The Hung Hom operator asked the public “not to leave recyclables at the door of the shop to avoid nuisance to nearby residents” over the festive period in a Facebook announcement on Saturday.

Leanne Tam Wing-lam, a Greenpeace campaigner, said the people who dumped the waste outside the shop were more at fault than the NGO that ran the recycling point.

“It’s a bad habit of Hong Kong people,” she said. “They will continue to leave garbage next to full trash cans even though they aren’t supposed to do so.

“After the garbage levy comes into effect, this could be a loophole.”

Free reusable food container vending machines set up at Hong Kong universities

Hong Kong residents will start to pay for solid waste disposal from April next year and residents of private buildings not part of large estates will depend on off-site recycling collection points to save on their garbage bills.

Steven Chan Wing-kit, assistant environmental affairs manager of environmental campaigner Green Earth, said the incident underscored the disadvantages of the replacement of the streetside coloured bins in urban areas with the Green@Community locations in June last year.

He added staffed collection points could better ensure only recyclables were collected, but that problems would still arise out-of-hours.

Chan said the government could open some recycling points during the Lunar New Year holiday to take waste generated by the festivities.

But he added public education should be designed to cut waste production and encourage reuse of the packaging of consumer items.

“Too often we first think about recycling everything, rather than reducing resource use,” Chan said.

“The ideal approach is actually to have more reusable products and reduce consumption from the outset.”