Somali authorities have arrested two people in connection with Saturday’s deadly bombing, which killed at least 300 people and injured hundreds more.
A Somali intelligence official who spoke on condition of anonymity said one of the suspects persuaded soldiers to allow a truck filled with explosives into the capital Mogadishu.
Reports indicate that the explosives were made from military-grenade components.
Local police said the truck bomb exploded outside a hotel in a busy intersection in the capital, setting dozens of vehicles on fire.
The bombing is considered to be one the deadliest in the Horn of African country in years.
No claim of responsibility has been made so far, though pointers indicate that it could have been staged by jihadist group al-Shabaab.
The militants have waged war on the Horn of African nation for close to a decade, aiming to enforce a strict sharia-based system of governance.
The conflict has killed tens of thousands and forced millions others to flee their homes.
Following the Saturday bombing, recovery efforts are on-going in the capital. Health officials on Monday issued a plea for blood donations to help the victims of the blast.
Engineers also began repairing roads that were damaged by the blast.