Police were at the scene in Luton after four alleged immigrants were spotted leaping from the back of a lorry this morning.
The incident took place at around 10.30am on Kimpton Road.
An eyewitness said: "A van delivering steel for the DART project pulled up on Kimpton Road and four refugees jumped out.
"They were male, black, and all wearing jogging bottoms and dark clothing.
"The lorry driver had no idea they were in there.
"They just stood next to the lorry. Bedfordshire Police are there now. There's two officers and a van.
"It happened about half ten, 11 o clock, and it looked like the lorry was Austrian.
"Police have detained them now on site. You'd be lucky if any of them [the four males] were 16. They were very young.
"It looks like they've handed themselves in.
"This is not a very good situation. We don't want another tragedy."
A Beds Police spokesman said: "We were called to Kimpton Road at approximately 10.30am to reports of immigration offences.
"Two people have been detained in custody and an investigation is on-ongoing."