Burglars made off with $30 million in historic California heist. Weeks later, no one's been caught.

An Easter Sunday heist led to a $30 million payday for a band of burglars, all of whom have so far eluded capture by federal investigators who are hunting them down. 

The daring operation sounds like something cut straight from an “Ocean’s 11” script. But that’s exactly what occurred in the early hours of March 31 while most people in the Los Angeles area were fast asleep. 

More than 20 days have passed since law enforcement officials were called to the money storage facility in the Sylmar area of the San Fernando Valley. In that time, investigators have remained extraordinarily tight-lipped about what, if any leads, they’ve uncovered that may help them solve what appears to be an elaborate crime. 

Reached Tuesday by USA TODAY, a spokesman at the FBI’s Los Angeles field office said the agency had no information to release to the media. The Los Angeles Police Department, which has indicated it is also part of the investigation, did not immediately respond to USA TODAY’s request for comment.

But while details are slim, some new insights have emerged into what many experts are calling one of the biggest cash heists in not only Los Angeles' history, but in the history of the entire United States. 

Here’s what to know about the brazen heist:

Florida crimes:Man killed girlfriend, then drove to police station with her body, reports say

$30 million California heist: What we know

Officers with the LAPD received a call for service at 4:30 a.m. March 31 to the money storage facility, which multiple news outlets have identified as GardaWorld, a global cash management and security company.

It's believed that the burglars stole as much as $30 million from the facility, making it one of the biggest cash heists in the city's history, according to the Los Angeles Times, which broke the news of the crime. That amount would also surpass any armored-car heist in Los Angeles, the outlet reported.

The complexity of the operation and the level of planning that appears to have gone into it suggest that an experienced crew was behind it.

A law enforcement source told the LA Times that detectives uncovered an effort to breach both the side and roof of the building, where cash from businesses across the region is handled and stored. Once inside, the burglars were able to find and break into a safe where money was stored without activating alarms, the outlet reported.

The missing cash was not discovered until operators of the business opened the vault the following Monday. Aerial footage from a KABC-TV news helicopter showed a large hole on the side of the building that appeared to be boarded up with plywood.

Security experts quoted in multiple news outlets have speculated that the heist likely took months to plan and almost certainly couldn't have succeeded without help from someone on the inside – either a current or former employee at GardaWorld.

“This is a planned offense that took a heck of lot of consideration and effort to put together," retired FBI special agent, Gannon University lecturer and crime author Jerry Clark told the Guardian. “Somebody had to have knowledge of the building and how much cash might be available at any one time.”

GardaWorld, the Canada-based company that also operates fleets of armored cars, did not immediately respond Tuesday to USA TODAY’s request for comment.

Do false alarms at GardaWorld ahead of the heist provide clues?

Separate alarms at GardaWorld’s Sylmar cash storage facility alerted authorities several times in the lead-up to the heist, according to multiple outlets.

One occurred just before 11:30 p.m. on March 30, the night before the heist, and was later deemed a false alarm, according to the LA Times, citing a police log first reported by TMZ. Another three alarms were set off on Easter Sunday, the first of which rang around 4:30 a.m. and appears to have drawn interest from investigators, who asked a neighbor if they had noticed "anything suspicious around 4 a.m.," the LA Times reported.

Hours after the alarm was triggered, a LAPD police car was dispatched to the property, a supervisor was notified and a report was written, the LA Times reported.

Aria Kozak, chief executive of L.A.-based security services company Elite Interactive Solutions, told the Times that the false alarms could have been the criminals testing the security system at the facility.

“They are very capable and smart and they will look for the soft or weak spot,” Kozak told the outlet.

What else are security experts saying?

Jeffrey Zwirn, a longtime security consultant, told the Los Angeles Times that the success of the heist appeared to be the result of “a systemic failure.”

Calling the theft "a shock," Jim McGuffey, an armored car expert and security consultant, told the Associated Press that any money-holding facility should have two alarm systems and a seismic motion detector right on the safe, along with motion sensors throughout the building. 

“For that kind of money, you don’t just walk in and walk out with it,” McGuffey told AP, adding that GardaWorld has a good reputation in the security industry. “A facility should be protected from the top to the bottom and the sides.”

Where the operation stands among other U.S. cash heists

The heist is now considered to be among the largest ever in the U.S. 

The prior largest cash robbery in U.S. history occurred in 1997 when five armed robbers in black clothing and masks robbed the Los Angeles Dunbar Armored Co. depot of nearly $19 million, according to the Los Angeles Times. While those behind the incident were eventually caught years later, most of the cash was never recovered.

Although not a cash heist, nearly two years ago, as much as $100 million in jewels and other valuables were stolen from a Brink’s big rig at a Southern California truck stop, the AP reported. Those thieves have never been caught.

Contributing: Saman Shafiq, USA TODAY

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at elagatta@gannett.com