Singapore on Tuesday filed charges against 24 Indian nationals who allegedly took part in its first riot for over 40 years, as officials and activists warned against inciting racial hatred over the incident. The men face up to seven years in jail plus caning for the hour-long fracas on Sunday night, triggered when an Indian construction worker was struck and killed by a private bus in a district known as Little India. They were among an estimated 400 South Asian migrant workers involved in the rampage that left 39 police and civil defence staff injured and 25 vehicles -- including 16 police cars -- damaged or burnt. The charge sheet said the men threw pieces of concrete and were "members of an unlawful assembly whose common object was to overawe, by a show of criminal force, police officers in the exercise of their lawful power to maintain law and order at the scene". The suspects, aged between 22 to 40, looked sombre as the charges were read in Tamil in court by an interpreter. They were remanded at a police complex for one week for further investigations. Police earlier said the suspects could be charged with a more serious offence punishable by up to 10 years in jail, but they faced a lesser charge on 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". Two Bangladeshis, another Indian national and a Malaysian also arrested after the riot were released because investigations showed they were not involved. 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. 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. 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. Officials have called for calm after the Little India riot, which triggered a wave of foreigner-bashing in social media. On the Facebook page of Yahoo! Singapore, reader Tan Beng Ming wrote: "Jail them, cane them and send them packing! For good measure, send their compatriots back too!" "Only foreigners will start a riot, it is their norm," wrote another reader, Koh Koh. Prime Minister Lee Hsien Loong urged Singaporeans Monday not to let the "isolated incident" tarnish their views of foreign workers, who number more than a million. Lee also ordered the formation of a special committee to review the factors that led to the riot, as well as measures to manage areas where foreign workers congregate. There will be a ban this weekend on the sale and consumption of alcohol in the area where the riot broke out following eyewitness accounts that many attackers were drunk. Activists have urged authorities to investigate whether the violence on Sunday was an indication of wider discontent among poorly paid migrant workers. "If these factors go unaddressed, the threshold for escalation remains low. The smallest incident gets to a tipping point quite easily," socio-political blogger Alex Au wrote. Russel Heng, president of welfare group Transient Workers Count Too, said in a commentary in the Straits Times on Tuesday that "I find the on-line xenophobic comments targeting foreign workers offensive". "If a majority of Singaporeans are reasonable fair-minded people, then I would urge every single one of us to rebuke, rebut or ignore the nasty xenophobes among us," he added.