The number of deaths from traffic accidents in the United States jumped 8.1 percent in the first half of 2015, suggesting smartphones and other driving distractions could be making America's roadways more dangerous, officials said on Tuesday.

Preliminary government statistics, released during a Thanksgiving holiday week known for heavy traffic congestion, showed deaths rising to 16,225 in the January-June period at a rate more than double an increase in overall driving spawned by falling gasoline prices and a growing economy.

"The increase in smartphones in our hands is so significant, there's no question that has to play some role. But we don't have enough information yet to determine how big a role," said Mark Rosekind, who heads the National Highway Traffic Safety Administration, the federal government's auto safety watchdog.