After an investigation, no explosive devices were found on board

Fighter jets escorted the planes to the runway, bomb squads preparing to sweep the cabins

Delta 1156 flew in from Portland, Southwest 2492 came from Milwaukee

Twitter user @KingZortic sent slew of threats to Delta and Southwest

The FBI is still trying to track down the Twitter user that made bomb threats targeting two jets bound for Atlanta, prompting F-16 fighter jets to escort the planes.

Special Agent Stephen Emmett said the agency is continuing to pursue leads in an effort to locate the individual responsible for the threats.

No bombs were found in searches of both planes after they landed safely in Atlanta on Saturday.

Scroll down for video

Was this the threat? It is believed this is one of the tweets that prompted the FBI raid of two airplanes

Warning: The Twitter user sent a slew of warnings to Delta and Southwest on Saturday

Threats: A Delta flight and a Southwest flight reported credible bomb threats as they landed at Hartsfield Jackson International Airport in Atlanta, Georgia, on Saturday afternoon

Emergency: Passengers were escorted off the flights that landed around 3pm before bomb squads boarded

It is believed the threats came from a Twitter user with no followers who goes by the name KingZortic.

The user sent a slew of warnings to Delta Airlines and Southwest Airlines on Saturday, claiming to have planted explosives on flights which were due to land at Hartsfield Jackson International Airport.

Bomb squads was rushed in as a result, but nothing suspicious was found on either flight.

One tweet read: '@DeltaAssist I have a bomb on one of your planes, but I forgot which one when I left the airport. Can you help me find it?'

Another said: '@SouthwestAir As part of a nationwide State agreement. A bomb was placed on SWA2492. It will be detonated at a random time of my choosing...'

It is believed these tweets prompted NORAD fighter jets to escort Delta flight 1156 and Southwest flight 2492 to the Atlanta, Georgia, airport.

Bomb squads then rushed about the Delta flight, which came from Portland, and the Southwest flight, which flew in from Milwaukee, with canines.

However after an investigation of both planes found there were no explosive devices on board.

Both flights had landed by 3pm and all passengers were being ushered off as bomb squads prepared to sweep the cabins, the Atlanta Journal Constitution reported.

FBI officials told WSBTV the passengers on both flights would be interviewed and searched before they are allowed to leave the area.

After the flights were airborne, the Twitter user King Zortic, who claims to be a member of a group they title The State, bombarded Delta and Southwest with warnings.

The user, who claims to be based in Chicago, wrote to Delta: 'I have a bomb on one of your planes, but I forgot which one when I left the airport. Can you help me find it?

'It was from Portland to Atlanta, I forgot the flight number, though. It was something like DL156 or DL 1556 I forgot the order.

'Oh yes, that's it. 1156, thanks. It was smuggled through one of the back entrences because the airport didn't... have much security around one of the entrences so the bomb is at the back of the plane. Everyone will know when it's detonated.

'I had one of the airport security help me because he's an old friend who now works for The State. No more information for you.

'If anything happens to me I'll make sure that more flights are targeted. I strongly suggest you don't try anything stupid.'

To Southwest, the user wrote: 'Hello, I need help.

Escorted away: Passengers leave a fire station as they board a shuttle taking them off the tarmac

Security: A police officer walks on the edge of the tarmac as bomb squads with canines search the planes

'As part of a nationwide State agreement. A bomb was placed on SWA2492. It will be detonated at a random time of my choosing...

'As you are the second and last aircraft of the day to be targeted. It's strongly recommend you don't try anything stupid.'

Following the FBI raid of both planes, the user tweeted: 'I'm going to get raided. Oh noeS!!'

Airport spokesman Reese McCrainie would not say how the threats were received, only that, 'we believe the threats to be credible,' the Journal reported.

A Southwest Airlines spokesman said: '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.