All the drivers had come to England through Dover.
A total of 39 males from Eritrea were detained, along with four from Sudan.
Essex Police contacted immigration officials to report 18 men (four from Sudan, the remainder from Eritrea) were arrested on suspicion of being illegal immigrants in Thurrock. A 44-year-old lorry driver from Sheerness was also detained.
Suffolk Constabulary confirmed it handed 25 people to the Immigration Service after they were found in Haverhill and Ingham, near Bury St Edmunds.
On January 13 six men were seen were taken to Bury police investigation centre after decamping from the rear of an HGV.
Last Saturday 19 males, including two children, were detained after being seen walking on the A134 from Ingham towards Thetford.
A Home Office spokesman said: “We work closely with the police to tackle illegal immigration and continue to strengthen the security of our border to stop those who have no right to enter the UK.
“In the year to April 2014 Border Force officers based at UK ports and at our juxtaposed controls in France and Belgium prevented more than 19,000 attempts to enter the country illegally – a rise of more than 60% on the previous year.”