Scary costumes on Halloween were not appreciated in Beijing, at least not on the subway.

Dressing up as a monster or frightening creature could be cause for arrest as authorities worried that it could cause other fearful passengers to "panic."

Expats in the Chinese city have organized Halloween parties on the subway itself for the past few years. During the weekend before Halloween, those dressed in costume would hop on the subway Line 2 with beer and mixed drinks in hand. When security guards would try to stop the group, they would evade the authorities by blending into the throngs of people, who were often dressed as subway security personnel.

Halloween is not a celebrated holiday in China, and the Beijing government discourages the superstitious practices. The Beijing Times ran a warning by authorities against scaring subway riders, as it could lead to panic.

Police said that if trick-or-treaters "insist on getting on the subway or the chaos is serious and causes a stampede or other public safety incident, the police will deal with it severely in accordance with the law."

Next month, Beijing will host the Asia-Pacific Economic Cooperation conference in November. This crackdown is part of preventative efforts to avoid a scandal before the biggest international event in the area since the 2008 Olympics, according to ABC News.

In preparation of the APEC summit, the Beijing government has been taking other measures on improving their city before leaders from around the world arrive. Factories in the immediate area have been shut down to improve air-quality. For the first 12 days in November, there will be widespread traffic controls and limits that cars can only be driven every other day, regulated through license plate numbers.

Many Chinese citizens spoke out in support of these Halloween regulations, expressing little sympathy for the seemingly frivolous partiers.

"Please consider children and old people in public places," an Internet commenter from Nanjing wrote.