Three inmates escaped from a Southern California maximum-security jail Friday, leaving authorities scrambling for answers.

“We’re talking about breaching, in some places significant amounts of steel, rebar and metal,” sheriff’s Lt. Jeff Hallock told the Associated Press. A defeat that required sophisticated tools from outside the jail.

After prison tailor Joyce Mitchell pleaded guilty to helping two upstate New York inmates Richard Matt and David Sweat escape last summer, the spotlight is being turned on employees in the Orange County jail who may have helped the three inmates escape Friday.

“We’re going to take a look at everybody who may have been assigned there,” Hallock told the Associated Press. “What I can assure you is that the compromises in security have been shored up.” He did not elaborate on any current in-house leads.

Although this is the second major jailbreak to make national news within a year, prison escapes are actually rare – and getting rarer - in the US.

In 2000, the Bureau of Justice Statistics reported 37.1 escapes per 10,000 prisoners. And in 2013, this rate had decreased to 12.7 escapes.

But even the rate of 12.7 escapees per 1,000 inmates is misleading. The Bureau of Justice Statistics groups together "escapes" and "AWOL" (Absent Without Leave) incidents to arrive at this total. While "escapes" classifies events like the New York jailbreak by Matt and Sweat last summer and Friday’s events in Orange County, AWOL’s are less exciting but more common.

AWOL can be attributed to a prisoner who comes back late from furlough or can’t be identified on a worksite for a few hours. AWOL and escaped prisoners are very different, but some states don’t differentiate between the two.

Looking exclusively at escapes, the national rate in 2013 was 10.5 per 10,000 prisoners.

“Out of the reported escapes in 2013, only three left a community work center, 16 walked off a work site, and one actually escaped from a security facility. The rest just failed to check in or meet some other requirement for their sentences,” CNBC explained in June.

And the overall rate of AWOLs and escapes has decreased during a time when the US incarcerated population is growing.

Over 2.2 million people were incarcerated in the US in 2014, and 2.8 percent of all adults in the US were under some form of correctional supervision accounting for probation, parole, and incarceration.

It has not been a steady increase; since the turn of the century some years have seen small decreases in the overall US incarcerated population. But over 85 percent of the decreases in the correctional populations are attributed to the decline of persons under probation, not the actual incarcerated inmates.

“It’s very rare – this happens very infrequently, which is why it’s such a story,” Martin Horn, professor of corrections at John Jay College of Criminal Justice at City University of New York, told USA Today after the New York escape last year. He says when he tried to analyze recent breakouts, “There weren’t even enough incidents to study.”

Hallock says Friday’s escape was the first jailbreak at the 900-inmate facility in over 20 years.

Jonathan Tieu, Bac Duong, and Hossein Nayeri were all held in Orange County Men’s Central Jail awaiting trail for violent, but unrelated, crimes. Tieu is accused of a gang-related murder; Duong of attempted murder and Nayeri of kidnapping and torturing in a drug deal gone wrong.

The escape wasn’t noticed for 16 hours, until a guard realized three inmates were missing from a 65-man dormitory during a 5 a.m. headcount Friday.

The three men used tools to first cut through the dormitory wall and into plumbing tunnels. Then again cutting their way through half-inch-thick steel bars, the prisoners made their way to the roof where they rappelled to the ground using ropes made of braided linens.

Federal authorities are now offering a $50,000 reward to anyone who may have information regarding the inmates’ whereabouts.

“We’re in a position where we absolutely need the public’s help,” Hallock told the Associated Press. “There’s people out there that know who these people are, who may have seen them. We’re asking for phone calls, whether it’s any piece of information you may have. We’re exhausting every lead that we currently have.”