Five people -- two drivers, two assistants and a passenger -- were placed under investigation after UN peacekeepers in Ippy, in central CAR, discovered several hundred shotgun cartridges hidden in containers and an unspecified drug.
The truck belonged to a subcontractor of Dubai-based company Ecolog -- a provider of services, including transport -- under contract with the UN in the CAR.
Four of the defendants were sentenced by a court in Bambari to terms ranging from six months to five years. They were also ordered to pay fines as well as symbolic damages of one franc to Ecolog, which had filed suit as a plaintiff, saying it had been a victim.
The February 14 ruling, seen by AFP, said "no blame" could be attached to Ecolog.
All UN materials transported by private companies in CAR are in sealed containers marked "UN", but the illegal goods were stashed within the cabin and chassis.
Pierre Die Chachay, the company's vice president of marketing and communications, said in a statement to AFP: "We fully support the court's independent decision to clear Ecolog of any involvement in the case and to hold the individuals culpable for their criminal misconduct.
"We are also satisfied with the court's declaration that Ecolog is in fact a victim and its decision that the individuals concerned should pay Ecolog a symbolic sum in damages."
He added: "Ecolog takes a zero-tolerance approach to any breaches of our ethics and compliance policies and we are satisfied that our approach of transparent and expeditious cooperation with the authorities in this case was correct in the circumstances. Nevertheless, as a responsible company, we take any incident as an opportunity to reflect on our practices. We will therefore be taking measures to reinforce all ethics and compliance policies internally and to bolster ethics, conduct and safety training for all our staff."
The CAR, where many armed groups continue to operate, has been under an arms embargo since a deadly conflict broke out in 2013.
The state has control over only a small part of the territory, while armed groups battle in the provinces for control of diamonds, gold and silver.
At the time of the incident, the country's strategic centre, between the towns of Bakala, Ippy and Bambari, was the theatre of several clashes between armed groups that form alliances according to the circumstances and local interests -- controlling mines, road racketeering and livestock theft.
Last month, deadly fighting in the capital Bangui involving UN troops left more than two dozen dead and around a hundred injured.