Urumqi (China), Sep 4 (Xinhua) Despite heavy security and patrolling helicopters, there was uncertainty among the residents of Urumqi in western China Friday morning following a wave of hypodermic needle stabbings and massive protests.

Helicopters were seen hovering over the city Friday morning, the second time since the July 5 riots that left 197 people dead.

“I bought a lot of food today (Friday). Who knows what will happen next,” said Luo Huanzhang who returned from the market on Guangming Road.

The market was crowded and many people intended to stock up groceries, Luo said.

Residents were also not keen to visit public places.

“I don’t know whether I should go to work,” said an employee with the Xinjiang branch of China Life Insurance (Group) Company, who only offered his surname of Tang.

Traffic controls imposed at 9 p.m. Thursday banned vehicles on major roads in downtown areas such as Youhao Road, Guangming Road and Renmin Square.

Chen, 28, a cloth vendor, said she closed her shop Wednesday as protests against the needle attacks flared up.

“People were so upset and unnerved recently. Doing business was almost impossible,” said Chen.

“My friends kept asking me to return to my hometown and I’m still thinking about it,” said Chen, who has lived in the city for 26 years since arriving with her parents from Chongqing in southwest China.

“My career is rooted here, I don’t want to leave,” said Zhang Shiying, who runs a construction material shop in the city’s northern area.

Zhang, a native of Beijing, opened his business in Urumqi 14 years ago.

The Experimental Primary School of Urumqi was closed Friday and it was unclear whether it would resume classes Monday.

Police in the capital of Xinjiang Uygur Autonomous Region have detained 21 people.

Authorities have issued arrest warrants to 196 suspects and prosecuted 51 for involvement in the riots, the regional government information office said in a statement Thursday.

The press office of the regional government sent mobile phone text messages to people Friday, saying the city had registered 476 people who had sought treatment for needle stabbings, of whom 89 were showing obvious signs of needle wounds. They comprised members of nine ethnic groups, including Hans and Uygurs.