Two people were injured in a rollover crash involving a fuel truck on the Trans-Canada Highway at Goldstream Provincial Park.

Mounties say the tanker collided with a white transit van on the highway just before Finlayson Arm Road just before 11 a.m.

The Trans-Canada Highway was expected to remain closed both ways until at least 4 a.m. Friday as investigators processed the scene. So far, it's unclear what caused the crash and police aren't saying whether speed played a factor.

"The investigation, right now we don't have a conclusion," said West Shore RCMP Const. Matt Baker. "These things are complicated and they take time, so once we know more information, then we'll be able to tell you."

The van driver was initially reported to be trapped inside the vehicle, but was later extracted with serious but non-life threatening injuries, while the truck driver suffered minor injuries, according to West Shore RCMP.

The Ministry of Environment initially said the fuel truck leaked an undetermined amount of furnace oil into a ditch, but response officers later said no oil was released from the truck. It said crews would transfer the furnace oil from the truck so it could be safely removed from the scene.

The ministry said roughly five litres of fuel did leak from the van due to a damaged gas tank, but Langford Fire was credited with mopping it up before it hit the nearby river. There was no impact expected to the environment, according to the ministry.

"The cause of the collision is under investigation. The fuel spill is a risk for motorists and first responders, as well as a potential environmental hazard," Cpl. Chris Dovell of West Shore RCMP said in a statement. "We ask for patience from drivers who are affected by any delays as emergency crews deal with the closure of Highway 1."

The truck belongs to small family business F.A.S. Fuels, which told CTV News the driver was injured and being checked out in hospital. It said the driver was returning from Nanaimo just after picking up the company's new truck and that the fuel tanks were not fully loaded.

Drivers are encouraged to check Drive BC for updates. Traffic was being diverted northbound at the West Shore Parkway and southbound at Shawnigan Lake Road. For those stuck in the crash area, there were detours available via Finlayson Arm Road and Millstream Road, but long delays were expected due to the amount of traffic. A longer detour around the crash was available via the Pacific Marine Circle Route.

There was a reported three-to-four-sail wait at the Mill Bay ferry terminal as drivers tried to detour around the crash through the Saanich Inlet. There was also a three-sail wait on the other side of the inlet at Brentwood Bay ferry terminal, according to BC Ferries.

As a result, the company added three supplementary round-trip sailings between both terminals leaving Brentwood Bay at 7:30, 8:40 and 9:50 p.m., and leaving Mill Bay at 8:05, 9:15 and 10:25 p.m. Those not already in the ferry line-ups weren't expected to get on, and BC Ferries recommended all other drivers steer clear of the terminals.

The Sooke School District also warned parents to expect school bus delays due to the crash and heavy traffic. Lengthy delays were expected for buses 4, 6 and 24.

Hazmat crews say it's the same corner of the Malahat Highway where a fuel tanker crashed in April 2011, spilling 42,000 litres of gasoline and shutting down the route for nearly 24 hours.

This is the scene at the Mill Bay ferry terminal has people try and get around Malahat closure. I've been told it's a 3 sailing wait. pic.twitter.com/Ol4hBXW5cl — Chandler Grieve (@CTVNewsChandler) May 24, 2018

Update: Wreckage of a van witnesses say a woman was just rescued from at Goldstream park. Just beyond a massive tanker truck is on its side. I can smell gas in the air. Malahat closed in both directions. Paramedics say two patients taken to hospital. Injuries unknown. @CTVNewsVI pic.twitter.com/vBIG2T13jA — Scott Cunningham (@CTVNewsScott) May 24, 2018

New photos from scene of fuel truck crash, spill on Malahat Highway at Goldstream Park. No ETA for reopening of highway #yyjtraffic https://t.co/tsSSzXrPuR pic.twitter.com/StCvX2FQZm — CTV News VI (@CTVNewsVI) May 24, 2018

Finlayson Arm Road has bottlenecked as drivers try to get in and out of Goldstream Park: https://t.co/tsSSzXrPuR #yyjtraffic pic.twitter.com/7pvkOfBPzy — CTV News VI (@CTVNewsVI) May 24, 2018