A child and a motorist died Wednesday evening in a single-vehicle crash on Interstate 35W, police said.
Speed was believed to be a major factor in the crash, police said. The young boy and adult male were wearing seat belts, according to police.
The names of the victims had not been released pending notification of relatives.
Police were searching for the driver of a 2008 to 2012 black Lexus with black wheels and lowered suspension which may have been in the area at the time of the fatal wreck.
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The accident occurred shortly before 7 p.m. Wednesday in the northbound lanes of I-35W near the West Oak Street exit.
Investigators determined a 2008 Ford F-250 was northbound on the highway traveling at high speed when it left the roadway and hit a guardrail, causing it to roll.
The driver was a man about 40 years old and his passenger was a boy about 10 years old, police said. Both were pronounced dead at the scene.
Police closed the northbound lanes of the highway for more than six hours as authorities investigated.
Investigators are searching for witnesses to the wreck.
Anyone with information should call Denton police at 940-349-7941.