Massachusetts ? Two commuter trains collided and derailed during the evening rush hour outside Boston on Wednesday, trapping and killing the operator of one train and injuring several passengers, authorities said.

The crash came just hours after an elevated train derailed in Chicago, sending several people to hospitals in a wreck that officials quickly blamed on operator error.

Investigators did not know what caused the Boston wreck, which killed the 24-year-old operator and injured about 10 passengers in an above-ground accident on the city’s “T” system near a station in suburban Newton.

Terrese Edmonds’ body was still trapped in the wreckage late Wednesday, and the operation to rescue her changed to a recovery mission, said Joe Pesaturo, a spokesman for the Massachusetts Bay Transportation Authority.