US government sources: Al Shabaab was behind a suspected bomb attack on a Somali passenger plane

Investigators believe a bomb most likely caused the explosion aboard a plane that was forced to return to the Somali capital of Mogadishu for an emergency landing on Tuesday, two US government sources said on Wednesday.

Investigators also suspect the Al Shabaab jihadist group was behind the attack, although no organization has taken credit for the apparent bombing.

There was no immediate comment from Al Shabaab, which has waged a gruesome insurgency against the Western-backed Somali government and a multinational African Union military force.

One person died Tuesday when the Daallo Airlines Airbus A321 carrying 74 passengers was forced to return after a blast tore a hole in the fuselage. Local authorities in the Balcad area, about 30 kilometers north of Mogadishu, said the body of a man, believed to have been sucked out of the plane, was found in the area.

Al Shabaab, an al Qaeda-aligned jihadist group that has been active in Somalia since 2006, has carried out regular attacks on officials, government offices and civilian sites inside of the country. It's also responsible for several major attacks in neighboring Kenya, including the September 2013 Westgate Mall attack in Nairobi, in which 67 people were killed; and the April 2015 massacre of 147 students at Garissa University, in western Kenya.

If al Shabaab is responsible for the airline blast, it would mark their first detonation of a bomb onboard an aircraft and the thrid significant attack in the past month.

On January 15th, al Shabaab overran a Kenyan military base in el-Ade, in southwestern Somalia, killing as many as 100 soldiers. The Kenyan military pulled out of el-Ade 11 days later, effectively ceding the territory to the jihadists.

The attack exposed alarming weaknesses within the African Union military mission, which has succeeded in removing al Sahabaab from Mogadishu and restoring the country's internationally recognized government. And it showed that despite territorial losses, infighting, and the death of key leadership, al Shabaab is still capable of mounting deadly against conventional military targets.

And on January 22nd, Shabaab gunmen stormed a beachside restaurant in Mogadishu, killing as many as 20 people.

Al Shabaab is still a formidable paramilitary force, with the ability to deliver an apparent battlefield defeat to a western-backed military. If it was responsible for the airline attack, it will have also shown that it's capable of launching sophisticated, ambitious, and potentially spectacular attacks on hard civilian targets as well.