Officers have detained a group of 10 men, following reports of 'suspicious activity' surrounding a lorry travelling to a Doncaster warehouse this morning.
The lorry is believed to have been travelling to a warehouse located in Rockingham Way, Redhouse.
A South Yorkshire Police spokesman said: "Police were called at 8.45am this morning to reports of suspicious activity surrounding a lorry at a premises in Rockingham Way, Redhouse.
"It is reported that a number of individuals were travelling inside the lorry.
"10 individuals have been detained by officers and currently remain in custody."
An eye-witness, who wishes to remain anonymous, said: "I saw a group of people who had tried to escape running off from the direction of the trailer in different directions to get away and then soon someone from the warehouse following them to try and catch up to them.
"Then shortly after the police had arrived and almost instantly caught around eight of them and then the search had carried on for around another 15 minutes with the police helicopter and dogs until they had caught the rest of the people who were running.
"Then afterwards during the investigation I saw the police recover the items of clothing and what looked to be like sleeping bags from inside the trailer of which they had to climb over pallets to get to."