By Ellen Wulfhorst

(Reuters) - More than 500 passengers spent the night on board Amtrak trains in northwestern Illinois, stranded due to the harsh winter weather, the U.S. passenger railroad said on Tuesday.

Three Chicago-bound trains came to a halt after running into impassable snow and ice on Monday afternoon, said Amtrak spokesman Marc Magliari.

The trains were the Southwest Chief from Los Angeles, the Illinois Zephyr from Quincy and the California Zephyr from the San Francisco area, he said. They were stranded about 90 miles from Chicago, he said.

Overnight temperatures were well below zero Fahrenheit (minus 18 Celsius) in the region, part of an arctic freeze that is gripping much of the United States.

The passengers had heat, water, lights and toilet facilities, Magliari said. Emergency workers were nearby, he said.

As of Tuesday morning, passengers on the first two trains, which spent the night on the tracks in Bureau County, Illinois were being taken to Chicago by chartered bus, he said.

Passengers on the third train, which spent the night in a train yard in Galesburg, would be moved by midday, he said.

"By about midday, nearly all the passengers from these trains will be in Chicago," he said.

(Editing by Scott Malone and Jonathan Oatis)