A Hong Kong Special Administrative Region (SAR) official on Monday called for building a peaceful, rational and orderly environment for the upcoming district election this week.

Cheung Kin-chung, the Chief Secretary for Administration, made the remarks at a joint press conference, saying all sectors of society are looking forward to a smooth running of the district election which is scheduled to be held on November 24.

He also slammed the "heinous" violence by the rioters, appealing to people to cut ties with the violent actions.

"The clashes in Hong Kong Polytechnic University yesterday were especially serious," Cheung told the media. "Since yesterday afternoon, the rioters near the university used deadly weapons, namely petrol bombs, arrows, steel balls and bricks to attack the police. Some police were injured by arrows and steel balls."  

"As the police warned, the extent of violence near Polytechnic University had reached the level of a riot, and anyone assisting the rioters could be considered to have committed the crime of rioting." 

At the conference, John Lee, the Secretary for Security, has warned of the potential dangers as "toxic and dangerous chemicals" had been stolen from the university laboratory.

"What's more worrying is that three universities have reported the loss of various chemicals. They are highly corrosive, acidic and toxic chemicals. If they are used to be made into weapons, they could cause fatal injuries," he said. 

According to Frank Chan Fan, the Secretary for Transport and Housing, the transport system has been damaged by the protests and the Cross Harbor Tunnel cannot be reopened in a short time.

With the ongoing violent protests in the region, all Hong Kong schools (including kindergartens, primary schools, secondary schools and special schools) will continue to be suspended on Tuesday due to safety concerns. 

The SAR government is evaluating that part of the schools can reopen on Wednesday, said Secretary for Education Kevin Yeung.