Fourteen migrants have been stopped in Boulogne-sur-Mer, northern France, as they tried to tried to leave the port aboard a stolen boat, heading for Britain.
The port authorities were alerted when people were seen trying to break into the boat, according to judicial sources.
The 14 migrants said they were from Iraq, among them a mother and her two children.
Police believe two people, possibly the traffickers, escaped when the others were stopped.
There has been a sharp increase in recent months in attempts by migrants to reach Britain by boat.
French and British authorities agreed on Sunday to beef up their attempts to halt the trend.
