Video footage purportedly shows the suspected bomber being given the computer after he passed through airport security. The blast ripped a hole in the Daallo Airlines plane shortly after takeoff from Mogadishu airport.
On Sunday, Somali intelligence officials released surveillance footage that appeared to show a passenger being given a laptop concealing the bomb.
Two other men - one of whom is wearing a security jacket - hand the computer to suspected bomber, the National Intelligence and Security Agency reported.
"The attack is believed to have been coordinated by a network of individuals, many of whom have been arrested and are being investigated," a Somali security official who asked not to be named told Agence France-Presse. He added that about 15 people have been detained.
The man who received the laptop is thought to have been blown through a gaping hole in the Daallo Airlines jet's fuselage when the device detonated at about 3,000 meters (10,000 feet) on Tuesday.
The aircraft survived the blast, which happened about 15 minutes after take off, but was forced to abort its journey to Djibouti and make an emergency landing at Mogadishu airport.
Initially, Somali authorities attributed the explosion to sudden air decompression. But, on Saturday, the transport and aviation minister admitted that a bomb had caused the 1-meter hole in the side of the Airbus A321.
The pilot said that if the explosion had happened when the aircraft was at a higher altitude it could have caused the jet to crash.
A passenger identified as Abdulahi Abdisalam was killed, probably after being propelled out of the aircraft by the explosion, investigators said. Another two passengers were slightly injured.
Daallo Airlines operates out of Djibouti, flying to destinations in the Horn of Africa and the Gulf.
The Qaeda-affiliated al Shabab group has been blamed for the blast.
mm/bw (AFP, AP)