Uncertainty was still stalking the streets of Urumqi, in western China, Friday despite heavy security and patrolling helicopters in the sky in the wake of a wave of hypodermic needle stabbings and massive protests.

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

"I bought a lot of food today. Who knows what will happen next," said Luo Huanzhang, who just returned from a regular morning outdoor market on the Guangming Road.

The market was crowded and many people intended to stock up groceries, Luo said. Residents also keep their forays into public places short.

"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.

People have to walk or cycle, but many chose to stay at home.

Bedclothes seller Chen, 28, said she closed her shop on Wednesday as protests against the needle attacks people 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.

Alip Toglak's restaurant on the Jianshexi Road had no customers for the last two days.

"This region is safe, please come to eat in my restaurant," the 50-year-old Uygur man pleaded with passersby.

"I will not shut down the restaurant. I hope life will return to normal soon," he said.

The Experimental Primary School of Urumqi, a first-class school in the city's south with more than 1,000 students, was closed Friday, and it was unclear whether it would resume classes on Monday, said Ding Lan, a 11-year-old student.

The management authority of the Appendant School of Chinese Academy of Sciences Xinjiang branch, in northern Urumqi, required parents to pick up their children on Thursday, said Xi Rui, a teacher with the school, which has 1,000 primary and middle school students.

She said the school had received an order from its superior authority to suspend classes on Friday until further notice.

A reporter with the Xinjiang Economic Daily said insiders with the Xinjiang Administration of Education had ordered the closure of schools on Friday, but it was unclear when they would reopen.

Xinjiang International Exhibition Center, the venue of the trade fair that used to attract crowds of business people from around the world, especially central Asia, saw tight security measures and fewer visitors Friday.

Passersby were asked to open their handbags and then have them scanned at the entrance of the exhibition center. Most of the participants walked a long way to the venue due to traffic controls.

Many indoor booths were vacant as company representatives did not show up and visitor flows dropped drastically. Many firms began to sell products on display at half price.

"No one came. It is unsafe in the city. The needle attacks are terrible," said a sales girl with Double Happiness Home Appliance Co., based in Zhuhai City of the coastal province of Guangdong.

Zhang Min, a native of Urumqi, said she visited the trade fair every year to order suitcases. "But people were scared of going out now, so the trade fair will be ruined," Zhang said.

A delegate from Usu City of Xinjiang said his team was told to limit their activities to within 300 meters of their hotels after the event closes every day.

Police in the capital of Xinjiang Uygur Autonomous Region have detained 21 people, of whom six are in police custody and four have been referred for criminal prosecution, said the regional information office in a mobile phone text message to the public on Thursday.

It also said the courts would hand down severe punishments to those found guilty.

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

The police have requested the procuratorate to approve the arrests of another 239 suspects thought to be involved in 140 crimes. Another 825 are being held in criminal detention, the regional information office said.

The press office of the regional government sent cell 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.

As of Friday, there had been no deaths reported and no symptoms had been found of infectious disease viruses or toxic chemicals.

(Xinhua News Agency September 4, 2009)