A critical Rhode Island bridge that was partially shut down over safety concerns in December will need to be demolished and replaced, Gov. Dan McKee said Thursday.

An independent review of the Washington Bridge — which carries Interstate 195 over the Seekonk River from Providence to East Providence and serves as a key gateway to Providence — found additional structural deficiencies requiring that it be replaced, McKee said at an afternoon press conference.

The state must replace both the bridge’s superstructure and part or all of the substructure, he said.

“We’re going to fix the bridge, we’re going to make it right, and we’re going to make sure we keep people safe,” he said.

McKee said his administration is investigating what led up to the need to shut down and replace the bridge.

“We will hold all responsible parties fully accountable,” he said. “The day of reckoning is coming and coming soon.”

Peter Alviti, director of the Rhode Island Department of Transportation, said the new bridge should be substantially completed with traffic flowing between March and September of 2026.

The cost to demolish and replace the bridge should come in between $250 million and $300 million, he said. The state is looking at a range of sources for the funding including federal grants.

During the demolition and construction of the new bridge, the state will reroute six lanes of traffic — three in each direction — on the eastbound bridge structure.

Alviti said the eastbound bridge is a separate structure. The state had a structural engineering company determine that it was safe to carry six lanes — and then had a second engineering company to review the first company’s work to confirm the bridge is safe, he said.

Alviti said the Department of Justice is conducting a separate investigation into the need to suddenly shut down the bridge.

The bridge carries nearly 100,000 vehicles every day.

The sudden westbound closure in mid-December initially wreaked havoc on traffic, turning a 40- to 45-minute drive into several hours, stranding commuters for hours and sending others veering off their normal path. Some schools closed and held classes remotely.

Built in 1969, the westbound portion of the Washington Bridge was rated as “poor,” according to the Federal Highway Administration’s National Bridge Inventory released in June.

The overall rating of a bridge is based on whether the condition of any one of its individual components — the deck, superstructure, substructure or culvert, if present — is rated poor or below.

Alviti had warned of the bridge’s poor condition in a 2019 grant application to rehabilitate the bridge and make improvements to traffic flow, writing that it was “nearing a permanent state of disrepair.”

The bridge has an inspection frequency of 24 months, according to federal data. State officials said it was last inspected in July.