Visitors line up to buy tickets for Shanghai Disney Resort.Zhang Peijian / For China Daily

On April 29 alone, the first day of the holiday, about 70 scalpers were caught, police said.

The scalpers, who flew to Shanghai from across the country, were selling fast passes for park rides for about 100 yuan ($15) to tourists unwilling to wait up to three hours in line.

"We try to catch these scalpers on peak days like May Day, while on other days police will figure out other ways to break the operation," said Shen Qing, public security chief at Shanghai Disney Resort.

The detained scalpers were lectured about the regulations during an eight-hour session, and promised they wouldn't engage in improper activities. They were also asked to write a letter of repentance.

Scalpers, commonly seen outside venues including hospitals, train stations and popular performances, buy tickets or book appointments in advance and then sell them at inflated prices.

At Shanghai Disney, one of the country's most popular holiday destinations, scalpers smelled an opportunity, both at the gate and inside the park, where the park gives priority passes for rides.

Police said scalpers have a clear division of labor: Some will identify target customers, while others stand in line inside the park to get fast passes to be sold later. These scalpers typically hold season tickets, so the cost of each entry into the park is low, police said.

However, many tourists found that they could not use the fast passes because they could only be used in conjunction with the gate tickets they bought.

To catch the scalpers, plainclothes police officers walked around the ticket office and the main entrance, and located scalping partners who lined up inside the park.

Shen said the number of scalpers at the resort is decreasing, but simply trying to control their behavior won't solve the problem.

"We now spend more time negotiating with Shanghai Disney Resort's representatives and asking them to strengthen their internal management, such as checking ticket information carefully," Shen said.

He Qi contributed to this story.