U.S. Geological Survey geophysicist Julie Dutton says the tremors on Tuesday afternoon appear to be an earthquake. The agency's website shows an earthquake centered in LaGrange measuring 2.7 on the Richter scale.
But Dutton also says such shaking can be caused by mining blasts. She says isn't unusual for the agency's monitoring equipment to pick up activity from blasts.
A worker at Hanson Materials Service in nearby McCook says the company was doing mining work on Monday, which included blasts in its quarry.
Residents in Westchester, LaGrange and Western Springs say the tremors lasted 1 to 2 seconds.
"It does feel like the earth is moving a little bit but it's more a shaking than a?it only last for a couple of seconds and then you hear the blasts right after," said John Depue. "It doesn't bother me at all any more."
No injuries were immediately reported.
The Associated Press contributed to this report. All rights reserved.