Singapore police have questioned nearly 4,000 foreign workers in a widening crackdown following the city-state's first riot in more than 40 years, officials confirmed Wednesday.

Three more Indian nationals have been detained and will be charged later Wednesday with rioting, in addition to 24 of their compatriots who were charged in court a day earlier with the same offence, which is punishable by up to seven years in jail and caning.

A police spokeswoman told AFP Wednesday that so far a total of 176 men had been taken to a police complex to have their statements recorded, without providing details of their nationalities.

Four men hauled up on Tuesday were released after investigations showed they did not participate in the riot, while another was released on bail.

The hour-long fracas on Sunday night, triggered when an Indian construction worker was struck and killed by a private bus in the Little India district, left 39 police and civil defence staff injured.

25 vehicles -- including 16 police cars -- were damaged or set aflame by the estimated 400 South Asian migrant workers involved in the rampage.

The 55-year-old Singaporean bus driver who knocked down and killed Indian construction worker Sakthivel Kumaravelu, 33, has been released on bail after being charged with causing death by a negligent act.

Activists have urged authorities to investigate whether the violence on Sunday was an indication of wider discontent among poorly paid migrant workers.

Interior Minister Teo Chee Hean said police had increased their presence in foreign worker dormitories and places where they congregate around the city-state.

"Investigations will continue so that all those who have broken the law will be dealt with strictly, firmly and fairly in accordance with the law," Teo, who is also Deputy Prime Minister, said in a statement late Tuesday.

Singapore's foreign ministry said it was working closely with the Indian High Commissioner (ambassador) "to facilitate consular access and support for their nationals, including legal representation".

The wealthy but tiny Southeast Asian nation of 5.4 million depends heavily on guest workers, with labourers from South Asia dominating sectors like construction.

There are nearly 700,000 foreign workers holding "work-permits", allowing them to work in certain sectors such as construction and shipping for two-year periods, subject to renewal, according to official data.

Sunday's riot was the second incident involving a large group of foreign workers in the past year.

In November 2012 171 Chinese bus drivers stopped work to demand better wages and living conditions -- the first industrial strike in Singapore since 1986.

Five of the drivers served jail terms after it was declared an illegal strike, while 29 others were deported without trial.