Somali intelligence officials investigating a bomb blast on a commercial jet released surveillance footage Sunday appearing to show a passenger being given a laptop in which the bomb was concealed.
The blast on Tuesday ripped a hole in the Daallo Airlines plane fuselage shortly after it took off from Somalia's main airport, killing one person and forcing an emergency landing.
The newly released surveillance footage shows the suspected bomber being handed a laptop by two other men, one of whom is wearing a security jacket, the National Intelligence and Security Agency (NISA) said.
"There are investigations going on and about 15 people have been arrested so far in connection with the incident," a Somali security official who asked not to be named told AFP.
"The initial investigation results indicate that the bomb was planted in a laptop and was carried by one of the passengers.
"A CCTV camera recorded some of the activities and the attack is believed to have been coordinated by a network of individuals, many of whom have been arrested and are being investigated," the source added.
The authorities had initially attributed the blast to sudden air decompression.
On Saturday, following investigations by Somalia and international experts, Transport and Aviation Minister Ali Ahmed Jama blamed a bomb.
The blast punched a one-metre (three-foot) hole in the side of the Airbus A321 about 15 minutes after it had taken off from Mogadishu heading for Djibouti.
A passenger identified as Abdulahi Abdisalam was killed, probably after being propelled out of the aircraft in the explosion, investigators said.
Another two passengers were slightly injured.
Serbian pilot Vladimir Vodopivec told a Serbian newspaper he immediately suspected a bomb, adding he was able to make a forced landing after the explosion did not damage his navigation system.
Daallo Airlines operates out of Djibouti, flying to destinations in the Horn of Africa and the Gulf.
Mogadishu airport is heavily fortified and adjoins the capital's main base of the African Union mission to Somalia, the 22,000-strong force backing the government in the battle against Al-Qaeda-affiliated Shebab insurgents.
The insurgents have lost ground since being routed from Mogadishu in 2011 but continue to stage regular shooting and suicide attacks.
On Saturday, Somali soldiers backed by African Union troops recaptured the key port of Merka from the Shebab, just one day after the Islamists swept into the city, the army and residents said.