The number of human trafficking cases in Northern Ireland has more than doubled.
A total of 41 potential victims were identified last year, 2% of all UK cases, the National Crime Agency (NCA) added.
People are used for sexual exploitation, forced labour and domestic servitude.
Stormont Justice Minister David Ford said: "The scale of human trafficking in Northern Ireland is still relatively low when compared to the rest of the UK, with referrals only making up 2% of the overall figure.
"That is not to say there is room for complacency. Human trafficking is an abhorrent crime and everyone can play a role in tackling it."
Last year the UK National Referral Mechanism received 41 referrals of potential victims of trafficking in Northern Ireland. This compares with 17 people in 2012 and 32 in 2011.
The DoJ said: "V ictims are often forced to live in cramped and/ or overcrowded conditions, they may be collected very early and/ or returned late at night on a regular basis, they may have inappropriate clothing for the work they are performing, and/ or a lack of safety equipment."
It said there may be a heavy security presence at the premises where they live or work.
"Victims' physical appearance may show signs of injury, malnourishment, and their general appearance may be unkempt.
"They may be isolated from the local community and/ or appear to be under the control or influence of others."