Todd Spitzer, a member of the Orange County Board of Supervisors, said Thursday that his panel only learned of Soriano's fugitive status from county officials via email earlier this week.
"This was handled incredibly nonchalantly," he said. "Why didn't the board know for more than a month? The only reason we found out about him was that he killed five people."
Ed Harrison, a spokesman for the Probation Department, declined to comment about why Soriano was at the Orange County juvenile facility or how he escaped.
Nevada prosecutor Brian Rutledge said police did search for Soriano's name in a national criminal database for fugitive warrants and turned up nothing.
"Authorities in California either didn't put his name into the computer or neglected to enter in the fact that he was a fugitive," Rutledge said.
Soriano was arrested Saturday after the SUV he was driving rear-ended a van on a freeway outside Las Vegas, police said. A truck driver told investigators that he saw Soriano and his passenger walk away from the crash site and then return before rescue crews arrived.
Soriano told the arresting trooper he had "too many" beers before the crash, according to an arrest report. Several beer bottles were found in the SUV, authorities said.
Results of a blood-alcohol test were pending.
The van was carrying a trio of brothers and other members of their family from California who had been visiting their sick father in Denver. They were headed home to Southern California to prepare for an Easter celebration.
Three brothers, one of their wives and a girl were killed. Troopers said most of the passengers in the van were thrown from the vehicle as it overturned in the desert. Two other people were injured and hospitalized.
Soriano, who had only scrapes and bruises, was being held on $3.5 million bail and is due back in court Wednesday. Abel Yanez, a deputy public defender, declined comment because he hasn't seen the charges against his client.
At his initial court appearance, Soriano told the judge he lives in St. George.
Late Wednesday, Spitzer sent a list of 14 questions to probation officials to find out how Soriano's case was handled. He wanted to know what attempts were made to find him, whether law enforcement was notified about the escape, and the protocol when such situations occur.
Harrison said an arrest warrant is sought through a sheriff's department, and police in the area where a facility is located are notified when someone escapes from a juvenile facility. Santa Ana police were checking to see if they had been contacted following Soriano's escape.
Harrison said he couldn't discuss Soriano's case history as a juvenile. He said he could provide information if Soriano was a fugitive, but he is now in custody.
Spitzer said he has called on the county's chief executive officer and law enforcement watchdog agency to review how probation officials handled the case.
"What did we do, if anything, and could we have done something to prevent this tragedy?" Spitzer said. "I don't have the answers. I've demanded the answers, but haven't gotten them."