Singapore is set to deport 53 immigrant Asians workers for their part in the city-state's recent riot -- the first in 40 years.

Police said they picked up the 53 people, all Indian nationals except for one Bangladeshi, in an island-wide sweep early Tuesday morning.

The men are being held in connection with the street disturbance in an area known as Little India where migrant workers congregate to drink and socialize.

The riot was sparked by news that a bus had knocked down and killed a 33-year-old Indian national, Channel News reported.

Deputy Prime Minister Teo Chee Hean was quoted as saying the government will "not tolerate such lawless behavior" and that the incident would be thoroughly investigated.

About 400 rioters clashed with 300 police and riot officers in a 2-hour battle that left cars including police vehicles burned out.

Commissioner of Police Ng Joo Hee said in a written statement that the 53 people "have been served with stern police warnings and immigration removal orders and will be repatriated to their home countries shortly."

Ng said the majority of the 53 have been in Singapore for less than five years and half of them worked in building and construction businesses.

In comparison to the first group, this group of 53 will not be charged in court as their involvement in the violence Dec. 8 "was assessed to be less egregious."

Police previously picked up 35 people suspected with attacking police officers and vehicles, damaging property and inciting others to participate. Police have charged 28 , he said.

Ng also said about 200 other people have been "assisting in our investigations," but their involvement in the riot was "passive and incidental." However, they have been allowed to stay in Singapore and continue working "on condition of continued good behavior."

Police continue to investigate the fatal traffic accident and an independent expert on accident reconstruction has been called in.

Immediately following the riots, Singapore's government said it will "take no chances" on a repeat of the riot, the worst social unrest since 1969, the London-based Financial Times reported. As a "first step" an alcohol ban around the riot area in the enclave was pronounced for the weekend only.

The rapid crackdown underlines how authorities are quick to maintain social harmony in the officially called Republic of Singapore, an island country of 275 square miles lying at the southern tip of the Malay Peninsula and about 80 miles north of the equator.

Singapore is grappling with its need for foreign workers to sustain its economic success while integrating them into the wider community, the FT reported.

About 1 million of Singapore's 5.3 million population are foreigners. It also has four official languages -- English, Malay, Tamil from the subcontinent and standard Chinese Mandarin.

Singapore's Business Times reported that Prime Minister Lee Hsien Loong is aware that social unrest spilling over onto the streets can make foreign investors nervous.

On a trip to South Korea, after the riots, Lee told reporters that the disturbances triggered much interest from abroad because it was an "unusual" event for the country.

Lee said he had met two South Korean investors who "wanted to have an interpretation [of] what I thought of it, what caused [the riot] and what the Singapore government is going to do about it."

He said the government and the people of Singapore should be "very proper" and measured in any response to civil unrest.

"Whether online or anywhere else, we have to exercise some restraint. The anxiety and the alarm is quite understandable," Lee is quoted as saying.

"But if we express ourselves in unrestrained, unreserved terms and sometimes xenophobic terms, even on the Internet ... I don't think that is helpful."