Delaware officials have ordered the emergency closure of the Interstate 495 bridge over the Christiana River in Wilmington after discovering that four of its support columns are tilting.

State transportation officials said Monday that four columns on the river's south bank are tilted by as much as 4 percent from vertical. They say the bridge is undergoing a complete inspection.

The 4,800-foot bridge normally carries about 90,000 vehicles a day on I-495, which diverts traffic around the city of Wilmington and toward the Port of Wilmington. The route parallels Interstate 95, which runs through downtown Wilmington.

Delaware Transportation Secretary Shailen Bhatt says he doesn't know just how long the bridge will be closed. But he warns of a "significant impact to the traveling public" until the issue is resolved.