PROVIDENCE, R.I. (AP) — Authorities have found a critical structural failure in one of the busiest bridges in Rhode Island and have closed its westbound side to begin a repair job expected to take months.

The Washington Bridge carries Interstate 195 over the Seekonk River from Providence to East Providence and serves as a key gateway to the state’s largest city. The Rhode Island Department of Transportation said Monday evening that a “critical failure of some original 1960s bridge components” was located in the bridge.

The repair work could take three months or more. All westbound lanes will be closed and traffic diverted at first, the agency said.

RIDOT said it will redirect traffic to two lanes on the eastbound side in the next two to three weeks.

The closures brought major traffic delays to the Providence area on Tuesday. The bridge carries close to 100,000 vehicles every day.