(CNN) -- Transportation authorities in Washington state hope to have traffic flowing again by mid-June along a critical highway corridor where a bridge collapsed last week, Gov. Jay Inslee said Sunday.
Thursday's collapse of the bridge on Interstate 5 over the Skagit River sent cars tumbling into the water and shut down a portion of the state's main artery to Canada -- one on which trucks carry an estimated $13.9 billion in U.S.-Canada trade cargo, according to U.S. Sen. Maria Cantwell. Three people were injured, and there were no fatalities.
The temporary solution developed by the state's Department of Transportation includes using steel girders at the site of the collapse while a permanent bridge is built. The permanent structure would be completed "sometime in September," Inslee said.
Inslee praised the quick development of the plan, noting the closure of the corridor for a significant period of time would hurt the area's economy and its residents.
Heavy traffic along Interstate 5 was reported in both directions at the start of the holiday weekend as cars and trucks inched along a cumbersome detour that took vehicles off the interstate and onto county roads. Roughly 70,000 vehicles travel that portion of the interstate a day, according to the state Department of Transportation.
Before work can be done, authorities must inspect the river's piers to ensure that they can hold the temporary bridge and must remove the remainder of the collapsed structure out of the water.
An initial investigation shows the 1,111-foot-long bridge collapsed when a tractor-trailer hauling an oversized load hit one of the bridge's overhead tresses, according to Deborah Hersman, chairwoman of the National Transportation Safety Board, which is investigating the incident.
CNN's Chelsea Carter, Ben Brumfield and Katharine Barrett contributed to this report.