Chilliwack RCMP Const. Tracy Wolbeck says police were called at 11:55 p.m. PT Sunday night to the intersection of McDonald Road and Ballam Road.
Police found one of the concrete barriers was pushed over, and a power pole had been sheared off, and officers followed the trail to the riverside, where they assumed a vehicle had gone in.
Wolbeck said that after a short search, police located the body of a 36-year-old woman — presumably the driver — in the river.
"This was very tragic," Wolbeck said.
The RCMP underwater recovery team was called in to continue the search.
"We are doing everything we can right now to look for any other possible victims," Wolbeck said.
"These searches can be very difficult emotionally on emergency workers and we are very hopeful that there are no further victims involved."
The vehicle, a Ford F-150 pickup truck, was pulled from the river Monday morning.
Police are not indentifying the driver at this time.