PARIS - At least 12 people, including five members of a family vacationing from Connecticut, were killed as fire engulfed part of an overnight express train from Paris to Vienna early yesterday.

The rail accident, which occurred just outside a station in the eastern city of Nancy, was France's worst in five years. The blaze drove trapped passengers to smash windows as flames shot high into the air. Nine people were taken to a local hospital, and police investigators and a team of psychologists converged on the scene.

The fire appeared to have started in an electrical control panel in a first-class sleeper car as the train sped through eastern France, local police officials said. The French national rail authority said the cause was under investigation.

Relatives provided the identity last night of the American victims, who lived in Northford, Conn.: Salvatore Michael Amore, 43, a Connecticut accountant; his wife, Jeanne, also 43; daughter Emily Jeanne, 12; son Michael Bernhardt, 8; and mother Susanne, 72.

French officials ascribed the deaths to asphyxiation and burns, saying that in addition to the Amores, the dead included three Germans, a Russian couple, a Hungarian man and a Greek woman. Among those being treated for smoke inhalation and burns at the local hospital were four Germans, two Britons, an American and two French nationals.

The train fire was first spotted outside Nancy by French rail officials who saw smoke pouring out of sleeper car No. 261 as the train passed through the station. They sounded the alarm and cut electricity to the rails, bringing the train to a halt. There, local firefighters quickly extinguished the blaze but could not save the victims. "We got there too late, and we found the dead," Jean-Jacques Horb, a firefighter, told reporters.

French prosecutors, who have opened an investigation, said the blaze was most likely accidental. "We can't rule out any theories for the time being," said the regional prosecutor, Michel Senthille. "Preliminary investigations indicate that, given the relatively small number of burns on the bodies, except for two who suffered burns on their extremities, the deaths were caused by asphyxiation."

All the dead were apparently trapped in the car. "The catastrophe was amplified by the fact that it was in a confined space," said chief firefighter Jean-Louis Modere. "The fire was limited, and the amount of smoke very quickly became catastrophic."