(CNN) The world's busiest airport has started screening employee bags before allowing workers into secure areas and shutting down access doors to the airfield in the wake of a gun-smuggling operation , CNN has confirmed.

Until recently, Atlanta's Hartsfield-Jackson International Airport had about 70 access points for what's called "back of the airport" employees, including baggage handlers and ramp workers. The workers were not subject to bag and body check screening when going to work.

Before the new measures, employees only had to swipe their badges to gain access to secure areas of the airport. Now private security guards are checking their bags and personal belongings before they are allowed to enter a security door at the main terminal.

"There's a phased-in approach to get to full employee screening," airport spokesman Reese McCranie said.

In addition, after a CNN inquiry, airport officials closed one access point to the ramp used by Delta Air Lines employees arriving for work on the lower level of the airport.

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The employees have to punch in an access code to the door, and once inside, swipe their badges to go through another door. They still have access to the outer door, but the second inside door that leads to the ramp is now restricted.

Delta subcontractors confirmed to CNN that employees could access the airfield after punching in their code and going through another door.

"Yeah, they can get into the terminal," the employee said. "The break room allows you to go through a door where they have access to the mezzanine. The mezzanine is the outside where the planes are, it's where they do their work. They have other elevators that they can go through that'll take them up to the terminal."

Within days of CNN's visit, the airport restricted access.

"The area that we visited ... that leads from the Delta break room to the baggage make-up area is being locked down," McCranie told CNN. "It will remain an emergency exit per fire code. If anyone tries to access it, the door alarm will be activated and recorded on CCTV (closed-circuit television). The only personnel that will now have access to this door will be emergency responders (police and fire department)."

Delta said that due to the sensitive nature of security protocols, it could not discuss specifics, but noted that "safety and security are always Delta's top priority and we are continually engaged with DHS, TSA and other stakeholders to enhance strategy and tactics across the airline's global operation."

Atlanta airport security checks employee belongings. (Photo by Yasmin Khorram/CNN)

The airport plans to reduce the number of employee access points from about 70 to 10, McCranie said. In addition, secure area access has been cut for about 4,400 employees who work for companies at the airport. Those employees will now have to go through Transportation Security Administration screening.

Federal agents broke up a gun smuggling operation at Atlanta's airport in December, arresting a Delta baggage handler and passenger. The baggage handler was able to bring guns to work in a satchel, enter the gate area and pass the weapons to a passenger who had already gone through security, according to an arrest warrant affidavit and officials. The passenger transported guns on about 20 Delta flights from Atlanta to New York last year, the affidavit said.

A CNN investigation found that only two major airports in the United States -- Miami and Orlando -- conduct full employee screening, requiring all employees with secure access to pass through metal detectors.

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Following a January congressional hearing about airport employee screening, the Atlanta airport's general manager, Miguel Southwell, said he wanted to move toward full screening.

"It can't be a one size fits all," Southwell said. "In addition to the background checks as an employee, there's an enormous amount of training that goes on. There's an enormous amount of retraining that goes on as well."