SEATTLE — The Seattle tunnel is now open to traffic.

Crews began the opening sequence Sunday about 10:30 p.m. and opened the northbound lanes Sunday about 11 p.m. The southbound lanes opened about an hour later. All ramps were open by Monday at 12:15 a.m., with the exception of the northbound State Route 99 off-ramp to South Dearborn Street, according to Washington State Department of Transportation spokesperson Laura Newborn.

That SR 99 off-ramp to the stadium district will take about one to two more weeks to complete, according to Newborn.

RELATED: What you need to know to drive the Seattle tunnel

WSDOT had hoped to fully open the roadway by the morning commute, and originally said that process could take several hours.

WATCH: WSDOT gives update as crews prep to open Seattle tunnel

Before crews opened the lanes, they were waiting for a final maintenance sweep to be completed. The sweep included removing garbage and paraphernalia from the tunnel celebration over the weekend, as well as making sure the tunnel and egress passageways were free of pedestrians.

Seattle police officers will be stationed at the new State Route 99 tunnel on- and off-ramps Monday to help show drivers where they need to go as well as direct cross-traffic. Officers will be at the north portal off-ramp at Republican Street and Dexter Avenue and the south portal on- and off-ramp at South Royal Brougham Way and Frontage Road.

Earlier Sunday, WSDOT opened the new intersection at South Dearborn Street and Alaskan Way as well as the new portion of Harrison Street that crosses Aurora Avenue North.

WATCH: Harrison Street opens ahead of tunnel opening

On Sunday morning, the Seattle Department of Transportation turned on the new signals at Harrison, Republican, and South Royal Brougham, according to Sowers.

RELATED: Step-by-step: Driving northbound on SR 99 after tunnel opens 

RELATED: Step-by-step: Driving southbound on SR 99 after tunnel opens