Hastie said she couldn't comment on what the specific problems were, but that engineers had been doing routine work when they came across something they "weren't expecting".
The New Zealand Shipping Federation is based in the building. Executive director Annabel Young said they were told there were safety concerns.
"We've all seen small cracks in the stairwell which I assume were post-Kaikoura earthquake.
"We were told that someone would be coming in to sort those little cracks out, but that they were superficial.
"The next thing that happened was that someone came into my office and said you have to be out by four."
Despite the sudden news, Young said she wasn't shocked.
"I mean, this is Wellington. The number of buildings that are empty because they're unsafe, the number of buildings that have come down - to be honest, in Wellington it's not a shock to be told that the building's got a problem.
"People outside Wellington don't understand the effect of the Kaikoura earthquake on Wellington."
Young is hopeful they'll be told on Monday that everything is fine, but she said it was impossible to predict.
The tenants have been told they'll be out of the building for at least 48 hours, by which time they'd be able to get more accurate information.
Many staff took office equipment with them when they left, and plan to work from home until further notice.