The container, which was infested with hundreds of the spiders, originated in Arizona, where the spiders are more common, The Mirror reported Saturday.
The container firm called in local pest control experts to get rid of the spiders.
"It is not something you expect to see, especially in the outback of Norfolk. Our guys are used to checking for wildlife, so when they spotted the spiders they shut the doors to keep them trapped in," said firm spokesman Mark Cook.
Black widows are the most poisonous spiders in North America, with venom 15 times more potent than a rattlesnake's. Their bites can be fatal.
"The little creatures have a bad reputation with people thinking their bite is immediately fatal, but generally people are just fairly sick," Cooke said.