Story highlights A truck driver collapses and dies after altercation with police

His death sets off a riot among onlookers who blame police

Five cars are set on fire during the unrest

Chinese authorities have arrested 20 people in the southwestern city of Luzhou after rioters, angered by the death of a truck driver who clashed with police, set cars on fire, state media reported.

The unrest, which took place Wednesday evening, also set off speculation on social media about whether the local government's version of events was accurate. That line of questioning was quelled when Chinese authorities prevented users from searching for terms related to the riot.

According to the official account published in the state-run newspaper China Daily on Friday, police approached the driver, Gan Junyuan, asking him to move his truck, which he had left in a no-parking zone while delivering fish to a market.

"Instead of leaving, however, Gan swore at, and scuffled with, the police," China Daily reported, attributing the version of events to Zhang Wenjun, secretary-general and spokesman of the Luzhou government. "During the scuffle, Gan suddenly announced he felt unwell, and shouted that his medicine was in the truck's cab."

When the police officers were unable to locate the medicine, onlookers stepped in and found it, helping Gan to take it, according to Zhang. But his condition deteriorated and medics were unable to save him.

By that time, a crowd of around 1,000 people had gathered around the scene, China Daily reported. Some of them became upset and attacked the police officers and their cars, it said. Five cars were set alight, two of which were burned completely.

It took until around 4 a.m. for authorities to deal with the unrest and for the crowd to dissipate, the newspaper reported.

It cited a local doctor, named Jie Si, as saying that the angry onlookers thought the police were at fault for what happened to Gan.

"People believe Gan agreed to leave after the police asked him to do so, and the truck scraped a policeman when he was backing up," Jie said, according to the newspaper. "In the ensuing scuffle, the policeman punched his neck. After he fell, the policemen thought he was pretending to be ill and left without calling an ambulance."

The conflicting accounts fueled doubts on social media about whether police were telling the truth.

"Only the victim and the police were clear of what truly happened," a user posted on weibo, the Chinese equivalent of Twitter, under the pseudonym Donglinanshan Farmer. "Now, only the police can talk. Who can guarantee that they're not lying?"

Discussion of the events became harder after authorities banned searches for terms like "Luzhou riot" and "Luzhou truck driver."

The local government didn't respond to calls seeking comment on Friday.