SINGAPORE — It started as a social media quest for breakfast dumplings, but ended with thousands of cyclists bringing traffic gridlock between two cities in central China.

What should have been a boost to the ancient city of Kaifeng’s economy backfired when the trend went viral - tens of thousands on rented bikes cycled through the night from nearby Zhenghou.

A six-lane expressway between the two cities quickly filled with cyclists as police took to loudspeakers urging them to leave. Bike rental firms warned they would remotely lock bikes taken out of Zhengzhou.

The event is part of a trend where young Chinese are travelling cheaply at a time when the economy is faltering and job prospects are scarce.

It began with four university students who cycled for 50km (30 miles) from Zhengzhou to Kaifeng in June to try guantangbao, a type of soup dumpling.

"You don't get a second chance at youth, so you must go for a spontaneous trip with friends," one of the four had told local media.

That message struck a chord with other young people in the city of 12.6 million - China's young have increasingly been complaining of burnout from an overly-competitive and grinding job market.

Thus was born the social media trend “Night Ride to Kaifeng".

State media initially praised it as a demonstration of young people's "passion". And local government saw it as an opportunity to recreate the instant fame that the town of Zibo enjoyed last year as millions arrived to sample its barbecues.

Before Friday night's gridlock Kaifeng's officials even announced discounts and events targeting college students. They also put in place additional traffic control measures to protect the cyclists.

"Everyone was beaming with energy and interacting with people around them. It was like back to my college days," 27-year-old Ms Li told the BBC.

She rode a motorbike to Kaifeng along with the students on Friday night. She said she decided to join and “live like a young person for once” after she saw a post about the trend.

There was heavy police presence all the way, she added.

"You could see ambulances and traffic police cars on both sides of the road quite often, and there were also drones flying above to monitor the traffic."

But the happy mood turned as the roads in Zhengzhou began to be overwhelmed by the thousands of bikes.

Pictures circulating online showed serious congestion on the main roads from Zhengzhou to Kaifeng. One witness told the local outlet Jimu News that his drive on that route, which usually took one hour, took three.

Some riders shared on social media that they were forced to get off their bikes and push their way through the crowd.

There was no official estimate of the number of bicycles on the road on Friday night. But reports on social media suggest the number ranged from 100,000 to 200,000.

And many of those who made it to Kaifeng didn't seem to have enjoyed the experience.

"I really regret going," said one viral post from a student, who rode more than seven hours. They couldn't get a taxi or a hotel room as the demand was overwhelming.

"As I sat in a restaurant eating my meal, I heard the owner criticising college students for having nothing else to do... I'm really sorry for affecting the people in Kaifeng," the student wrote.

Some users criticized the cyclists for "irresponsible" behavior such as littering.

As the gridlock worsened, three major bike platforms in China issued a joint statement urging students to use trains or buses for long-distance travel and avoid using bikes at night for safety reasons.

By Saturday afternoon, the companies had begun charging those who rode to a different city.

Multiple social media posts suggest some universities in Zhengzhou have asked students to return to their dormitories and imposed restrictions on them leaving the campus.

Traffic police in both Zhengzhou and Kaifeng closed off some of the main cycling lanes between the two cities on Saturday and Sunday.

It is not surprising to see officials in both cities pushing back because Chinese authorities have always cracked down on large gatherings, which they fear can lead to protests or any form of political expression.

Last month, police in Shanghai silenced celebrations for Halloween over fears the revelries might be used to express dissent.

Ms Li says spontaneous gatherings - such as the Night Ride to Kaifeng - will keep happening simply because they appeal to young people.

"People are so stressed these days, so these events are a good thing," she says. "Because happiness is infectious." — BBC