The search is on for the person who claimed bombs were on board two Atlanta-bound planes, WSB-TV reports.

Fighter jets escorted two planes to Hartsfield-Jackson Atlanta International Airport on Saturday afternoon, where they were met by a bomb squad and federal agents.

WSB-TV's Mark Winne broke the news of the bomb threats on Twitter.

Delta Flight 1156 was coming to Atlanta from Portland, Oregon. Southwest Flight 2492 was heading to Atlanta from Milwaukee. Both landed safely at the airport.

Winne talked to FBI Special Agent in Charge Britt Johnson on Saturday evening.

Johnson told Winne the initial threat was posted to Twitter, and that prompted authorities to act quickly.

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He said the FBI investigated and interviewed passengers. He said they are determined to find the person who sent the tweets.

No arrests had been made as of Saturday night.

Southwest Airlines released the following statement Saturday afternoon:

"Due a security situation, the aircraft operating Flight 2492 was taken to a remote area of the airport where customers and the aircraft are being rescreened. Our No. 1 priority is the safety of our customers and people. We cannot comment on the nature of the security situation."

Delta PIO Morgan Durrant told WSB-TV that there is always an ongoing concern about security. He said he could not comment on the threats.

He did say that Delta Flight 1156 was taken to a taxiway at the airport to have officials sweep the plane for security. He said the plane was inbound to Atlanta from Portland and that Delta would rebook passengers who needed connections.

WSB-TV's Tyisha Fernandes talked about the ordeal with some of those passengers, who said they were not told much at the time.

“You could look out the window and see people with machine guns and all sorts of threatening things (and) bomb-sniffing dogs,” passenger Joe Larkin told Ferenandes.

Just before 3 p.m. Saturday, a Twitter user tweeted Delta directly, saying, “I have a bomb on one of your planes, but I forgot which one I left at the airport. Can you help me find it?”

Delta replied, “Where did you leave the bomb?" The user answered, "It was smuggled through one of the back entrances.”

FBI agents said they are now on a manhunt to find the Twitter user who posted the threats.

“Typically on these things, there's a trail. Whether you want ... to or not, you leave a trail,” Johnson said.

The planes were both already headed to Atlanta, when they were guided by fighter jets to the airport’s tarmac. Once at the airport, officials hooked up what they call "rolling tarmac stairs," escorted passengers off the planes and immediately let the bomb-sniffing dogs screen the carry-on luggage from the flights.

“There was a process about going through the bags and so forth, and then we got on a bus and then they transferred us to one of the fire department houses,” passenger Brian Bennett told Ferandes.

The airport firehouse served as a command post while federal agents cleared everyone.

The FBI-led Joint Terrorism Task Force is investigating the threats, Johnson told Winne.

He said it is too early to call the incidents a terror threat.

“We’ll be going through all the feeds and onboard Wi-Fi,” Johnson said.

He said whoever posted the threats has committed several federal crimes.

Atlanta police, the Georgia Bureau of Investigation and Federal Air Marshal Service were among the agencies that responded to the threats.

Incoming and outgoing flights were initially delayed at the time.