A commuter train derailed on Chicago's South Side, killing at least two people and injuring more than 80, some of them critically.

The double-decker Metra train was travelling from Joliet to Chicago on Saturday when the locomotive and its five cars jumped the tracks about 8 kilometres south of downtown, authorities said.

Both victims were women, a 22-year-old who died on the train and a 30-year-old pronounced dead later at a hospital, said Judy Pardonnet, a spokeswoman for Metra, the commuter rail system that services the Chicago area. Seventeen of the injured were in serious or critical condition, said Assistant Deputy Fire Commissioner Raymond Orozco.

It wasn't immediately clear what caused the cars to derail.

All the track signals were working, and the track had just been inspected on Thursday or Friday, Pardonnet said. The National Transportation Safety Board was sending a team from Washington to investigate.

In all, 185 passengers and four crew members were on the train when it derailed in a neighbourhood of homes and businesses. The tracks are on a raised embankment next to a street, but none of the cars fell. Firefighters had to raise ladders to the track to reach the scene.

Dozens of emergency vehicles and two medical helicopters were called in, and workers put up three red triage tents to treat people near the tracks. City officials also called suburban emergency teams for help, said Fire department spokesman Larry Langford.

After the derailment, there was a 9-metre gap between two of the cars, one of which had severe damage at the front end. The other cars remained upright but had left the tracks.

The engineer was "badly shaken" and taken to a hospital for routine drug tests, Pardonnet said. He has been operating Metra trains for 45 days, following six months of training that included trial runs on the same Joliet-to-Chicago route, and also spent more than five years as a CSX Corp freight train engineer, she said.

Source: China Daily