Labour Day confusion surrounding the hypermarket's opening hours has led to scores of disappointed customers unable to get into the store or even fill their tanks with cheap petrol after Google led them to believe it was a regular shopping day.
It even saw a store manager break the news personally as the growing throng lined up for a 10am opening.
Unlike many stores, Costco is closed on public holidays including Labour Day, Boxing Day and Matariki.
However, the closure was not clear on the store's google business site, with a key word search of opening hours showing normal trade, while another link to the Costco store showing a vague reference that hours might differ on the public holiday.
"The store is closed yet their Google business website does not communicate this," said a bystander who did not want to be identified.
"Sadly people have come from far to this and crowds continue to form outside the front door. There is a tiny sign of you look in the entrance window which states closed Labour Day.
"Even an employee turned up just before 10am with the crowds confused."
The bystander said the car parks were also open so people were driving in only to find they had to leave. An hour later people were still arriving believing that the store was open.
A Facebook dedicated to Costco shoppers said there were reports that some motorists were removing cones in front of the petrol station to gain access even though the pumps were not operating.
"Just a friendly guys that Costco is CLOSED today. There is no access available to the petrol pumps and no access into the warehouse," said the post.
The bystander said a store manager addressed the growing crowd just before 10am saying the store would not be open.
"For a massive corporate this is a fundamental customer communication piece gone wrong," she said.
At midday the Costco Wholesale New Zealand Facebook page posted it was not open on Labour Day.
"We're closed for Labour Day today. We'll see you back in the warehouse tomorrow!" it read.
Customers were also alerted to the day-long closure on a bright banner on the official Costco website.
Costco has been approached for comment.
