A woman was seriously injured when her car collided with the back of a tractor-trailer on I-75 Thursday afternoon, Cherokee County officials said.

The sheriff’s office is still trying to track down the driver of the big rig, who did not stop after the wreck, according to Cherokee sheriff’s office spokesman Capt. Jay Baker.

The incident happened about 1:15 p.m. on the interstate between the Woodstock Road overpass and the Cobb County line, Baker said.

Witnesses said the woman’s black Honda Civic was merging lanes when it clipped the back of a white tractor-trailer, according to Baker. The impact caused the woman to lose control of the car and sent the Honda into a tree, Baker said.

Baker said the woman was not wearing a seat belt at the time of the wreck. She was taken to Wellstar Kennestone Hospital with serious injuries, he said. Her name was not released.

“It is possible the driver of the tractor-trailer was unaware the Honda made contact with the trailer,” he said.

Authorities ask anyone who might be able to identify the big rig or the driver to call the sheriff’s office at 678-493-4080.

An investigation is ongoing.

In other news:

Two metro Atlanta women, who are preparing to sue a company that sells dog treats, are trying to warn pet owners after their pets died.