A 19-year-old man and a 2-year-old girl are dead after their car hit a power pole on the Tasman Highway near Sorell late last night.
A woman, who was thrown from the wreck along with the driver, was rushed to hospital following the single-vehicle incident.
It takes the state's road toll to 27.
"At this time police were conducting a static Random Breath Testing site on the Tasman Highway Midway Point at the round-a-bout with Penna Road," said Senior Constable Kelly Cordwell.
"Eastbound traffic was stopped at the round-a-bout. A silver coloured Holden Vectra, travelling westbound also stopped in the line of traffic. The Vectra which was being driven by the 19 year old male completed a U turn and travelled back towards Sorell overtaking other vehicles.
"Just west of Nash Street, Sorell the driver of the Vectra lost control and the vehicle impacted with a pole on the northern side. The impact caused the vehicle to break into two. The rear of the vehicle remained in contact with the pole and the front came to rest in the west bound lane.
"On impact with the pole the rear of the vehicle caught fire and was engulfed in flames. Unfortunately the toddler who was in the rear could not be saved."
The highway remains closed and traffic diversions via Penna Road are in place.
Crash investigators are keen to hear from any motorists who had been stopped at the RBT at the time.