Newark, N.J. ? A massive power outage on Amtrak’s busiest corridor Thursday stranded tens of thousands of passengers for hours in hot, smelly cars – some in tunnels under the Hudson River – in the latest of several recent embarrassments for the perpetually money-losing railroad.

The cause of the outage, which created widespread disruptions from Washington to Boston, had not been determined Thursday.

Power was out for nearly three hours, affecting the nation’s federally subsidized passenger railroad and commuter lines in New Jersey, Maryland and Pennsylvania. Many passengers simply climbed out of stuck rail cars and walked to the next station.