Texas ? More than 500 soldiers and other searchers walked side by side in scorching heat Monday, looking for any sign of a soldier lost for nearly three days in the juniper-covered hills of the fort’s training range. They came up empty.

Sgt. Lawrence G. Sprader, 25, told his commanders by cell phone that he was lost late Friday, after he was two hours overdue in a solo navigation training drill.

He didn’t indicate he was sick or distressed at the time, but his phone’s battery has since died and searchers were worried that he had succumbed to the 90-plus-degree heat.

Besides searches on the ground, all-terrain vehicle operators and two Army Black Hawk helicopters were scanning the 15,000-acre training area day and night. By Monday night, roughly 9,500 acres had been searched.

The ground search ended at nightfall on Monday, but the helicopters were expected to fly all night. Ground searchers were to return this morning.