"We're extremely interested in that because that changes the dynamics of the whole accident," Highway Patrol Officer Steve Henry said Tuesday.
"We want to explore everything. That same amount of investigative focus is not on the other driver," Henry said.
Investigators also have not been able to determine if either driver was insured. Flores' driver's license was expired, making him unlicensed, Henry said.
Flores was driving west on Highway 78 eight miles east of Ogilby Road about 11:30 a.m. Friday in a sedan when he passed a slower-moving car in a dip in the hilly terrain. In the car with him were Arthur and Arthur's brother, Juan Luis Villavicencio, 6, of Blythe. Juan Luis was in the front seat. Arthur was in the back, although information on whether he was in a child-safety seat was unavailable.
At the crest of the hill, Flores' car crashed into the sport-utility vehicle driven by Jesus Castro Castro, 51, of Holtville.
The vehicles struck head-on in the eastbound lane, killing Flores, Juan Luis and Castro.
David and Anthony Jimenez were in the sport-utility vehicle driven by their father. Also in the sport-utility vehicle was Socorro Castro, 57, and Jesus Castro's companion, Raquel Jimenez Castro, 40, both of Holtville.
Socorro Castro died en route to Palo Verde Community Hospital in Blythe.
Raquel Castro was taken to Palo Verde Community Hospital. She was kept overnight and released Saturday, said hospital administrator Vickie Clark.
Other Castro family members were following the sport-utility vehicle in another car and witnessed the crash, investigators have said.
John Paul Flores was the uncle of Juan and Arthur. The car Flores was driving was registered to Juan and Arthur's mother, Veronica Flores of Blythe. She is a state prison correctional officer in Blythe. The boys' father lives in Imperial. Flores was taking the boys to their grandmother's house in Calipatria at the time of the crash, officials have said.
The only person in the crash to escape relatively unscathed was Luis David Delgadillo, 2, who lived with Socorro Castro, according to the Highway Patrol.
Some fragments of glass were embedded in Luis' eye but he was walking around after emergency crews arrived. He was taken to Palo Verde Community Hospital and later transferred to Loma Linda University Community Medical Center, where he was to be treated by an ophthalmologist, Clark said.
A hospital spokeswoman at Loma Linda said Luis was treated and released Saturday from the emergency room there.
All the occupants in the sport-utility vehicle were wearing seat belts. Emergency crews could not determine whether the occupants in Flores' vehicle were wearing seat belts.
Staff Writer Marcy Misner can be reached at 337-3441.