UPDATE 1.30PM: Police believe a four-wheel-drive heading south has crossed into northbound traffic in a crash that has caused extensive Bruce Hwy delays.
Nambour Forensic Crash Unit officer-in-charge Sherryn Klump said it appeared two sedans heading north were then involved in a resulting crash.
Emergency services were called to the Forest Glen scene, just north of the Nambour Connection Rd overpass, about 11.40am Saturday.
"The situation as we know it is that a southbound four-wheel-drive has left his travel lanes and crossed the table drain into the path of some north-bound vehicles," Sergeant Klump said.
She said two occupants of one of the sedans were trapped in their vehicle and needed to be freed by firefighters.
"They have been conveyed now to the Sunshine Coast University Hospital with injuries believed not to be serious or life-threatening," Sgt Klump said.
She said the occupant of the other sedan was also taken to Sunshine Coast University Hospital.
A Sunshine Coast University Hospital spokeswoman said one of the patients was in a serious condition and the other two were in a stable condition.
Northbound Bruce Hwy traffic was completely blocked and diverted through Nambour as a result.
"We thank our drivers who have been involved in that for cooperating.
"Southbound traffic doesn't seem to have been affected at all which is fortunate."
Sgt Klump said police were speaking with the driver of the four-wheel-drive about why his vehicle crossed to the wrong side of the highway.
"At the moment we have got to entertain all possibilities as to why that vehicle left a travel land and crossed over into the northbound traffic.
"The driver of that four-wheel-drive wasn't injured and he has been cooperating with us to this point.
"We will have to speak with him again at a later date."
The highway has been reopened to northbound traffic.
EARLIER: The Bruce Highway's northbound lane has been closed just north of the Nambour Connection Road after a serious three-car crash.
Police said the crash happened when a vehicle travelling crossed over the median strip into the southbound lane just before 11.30am.
Details remain thin, but it appeared two other vehicles crashed as a result, with the occupants of one vehicle getting trapped and needing to be cut free by firefighters.
A Queensland Ambulance Service spokesman said three people were taken to the Sunshine Coast University Hospital in a stable condition.
However, motorists heading north on the highway faced a frustrating wait while emergency crews worked to clear the road.