The seven were given prison terms of up to nine years each less than half the punishment demanded by prosecutors. They were acquitted of manslaughter by the three-judge panel, who ruled the defendants never intended to kill the migrants.
Two men were acquitted of all charges and walked free.
Defense attorneys said they would appeal.
The bodies of 54 men and four women were discovered June 18 by customs officials in Dover, England. Only two Chinese survived the ferry crossing from Zeebrugge, Belgium.
A British court last month sentenced the truck driver, Dutchman Perry Wacker, to 14 years imprisonment.
The verdicts announced in the Rotterdam district court by Judge Jos Silvis underscored the difficulty faced by European authorities in punishing traffickers who charge tens of thousands of dollars for a single trip to the West.
The European Union estimates a half million illegal immigrants enter its 15 member nations every year, coming from Eastern Europe, Latin America, Africa and Asia.
Two defendants Gursel Ozcan, a Turkish national, and Haci Demir, a Dutch resident of Turkish origin were convicted of running a human trafficking ring that smuggled three loads of illegal immigrants from mainland Europe to Britain between December 1999 and June 2000.
They received nine-year prison sentences and were fined $38,000 each. The other five men received sentences ranging from 30 months to seven years for assisting in the operations.
"Human traffickers abuse the desperate position in which these people often find themselves," Silvis said in court. "They abuse their dependence and supply transportation, acting out of greed."
The greed of the smugglers threatened the safety of "human beings who have no other choice" but to risk their lives, Silvis said.
The court found that defendants provided shelter for the immigrants in the Netherlands and Belgium and arranged fake documents and transportation.
The defendants filled the opening of the cargo container with crates of tomatoes and sent them on their fatal journey across the English Channel.
In rendering the verdict, Silvis said the defendants were "guilty of gross negligence" because they were aware of the risk of death and failed to prevent it.
As the cargo crossed the Channel, the driver ate dinner and watched movies while the migrants died in the container parked on the ship's deck.
The Dutch trial lasted less than a week, and only four witnesses took the stand. Much of the evidence came from the British trial, including statements from the two survivors.
The nine defense lawyers spent several days questioning police investigators about their investigation. The lawyers suggested police knew about the shipment but let it proceed o gain evidence against the smugglers.
The court rejected the claims, saying "there was no question whether the police new about the June shipment."
However, prosecutors and Justice Ministry officials acknowledged the gang's leader had been under surveillance for months. They have also admitted letting through shipments of drugs to bolster other investigations.
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