Emergency services were called to a multiple-vehicle crash near Pwllheli on Friday which closed a main road.
Three cars were involved in the "serious" collision along the A499, close to the Penrhos Polish residential home, just after 19:00 GMT.
North Wales Fire and Rescue crews from Abersoch and Pwllheli were called while police said the road would be closed for "a considerable amount of time."
Motorists have been advised to avoid the area from New Street to Beach Road.
It was along the same stretch of road where a 17-year-old was airlifted to hospital following a crash on Thursday.