The death from Monday's pileups in rural Illinois rose to seven, Illinois State Police said in a statement.
"The severity of the crash masked the remains and what was previously believed to be the remains of one individual was two," the agency said.
Officials said vehicles were so mangled, with some in flames immediately after the pileups, that criminal investigative techniques have been deployed to identify some of the victims.
"Due to the severity of the crash and the fire, we have activated our crime scene services and traffic crash reconstruction units," state police said by email Tuesday.
Thirty-seven other people, ages 2 to 80, were hospitalized with injuries from minor to life-threatening, Illinois State Police said earlier.
The collisions, reported just before 11 a.m. Monday, involved 72 vehicles in multiple pileups along a 2-mile stretch of Interstate 55 north of Farmersville, state police said.
"The cause of the crash is due to excessive winds blowing dirt from farm fields across the highway leading to zero visibility," State Police Maj. Ryan Starrick said at a news conference.
Involved in the collisions were two big rigs that had been on fire, as well as other commercial vehicles and passenger vehicles, the latter of which composed a majority of the wreckage, Starrick said.
All the dead were found in northbound lanes, state police said in their latest statement, although there was also wreckage on the southbound side.
One crash victim was identified as 88-year-old Shirley Harper of Franklin, Wisconson, according to the statement. Others were expected to be identified by the Montgomery County Coroner’s Office in the coming days.
The first pileup was reported on the northbound side of the interstate, which runs through farm country. Starrick said topsoil and dust from nearby farms were blown across the roadway.
"This is not uncommon," Starrick said. "This has happened before in various parts of the state of Illinois."
However, he said, the number of vehicles and casualties was unusual. A Montgomery County Emergency Management Agency official said at the news conference that it was difficult to reach the injured because some vehicles were on fire when first responders arrived.
The National Weather Service on Monday forecast "widespread blowing dust," with gusts of 34 mph possible, for the Farmersville area. Winds were out of the northwest, federal forecasters said.
The interstate reopened Tuesday morning after north of Farmersville overnight so wreckage could be cleared and investigators could examine the scene.
Farmersville, a small town along a defunct stretch of Route 66, is about 25 miles south of Springfield.