Middlebury Police Chief Richard Guisti said 60 to 70 people were evacuated from their homes and were taken to a shelter at the Fire Department.
Guisti said the highway, one of the main routes from Massachusetts into New York state, would remain shut down for most of the day.
"We're waiting for a company out of Massachusetts to attempt to unload the vehicle before we can have it removed from the site," Guisti said.
He said the I-84 shutdown meant local roads in his town and Waterbury were congested almost immediately and one, Connecticut 64, a main thoroughfare in his town, remained almost at a standstill five hours after the truck overturned.
One of those caught in the traffic jam was U.S. Rep. Rahm Emanuel, D-Ill., who was headed from New York to Hartford for a fundraiser for Rep. Joe Courtney of Connecticut.
"We're just in one long snake-line here," he said in a cell phone conversation with Courtney and reporters.
State police said the driver of the overturned truck suffered minor injuries.
