"A person has been spoken to and the area searched, and as a result Police can confirm there has been no threat to the Homegrown festival or the public.
"While the concern in this case appears to have been an innocent misunderstanding, Police would like to remind people to stay vigilant and call 111 if they see anything suspicious."
Concertgoer and Newstalk ZB reporter Emme McKay was at the main stage when they were told to evacuate. No explanation was given and there were no obvious signs of danger.
There are five stages at the Wellington waterfront festival beside Te Papa, and the other stages were not evacuated.
A minute's silence was scheduled to be held at 9.25pm but McKay said it did not appear to be related because people had been sent out of the venue.
She said everybody had been sent out to the New World carpark.
Homegrown PR manager Kelly Wright said earlier police had led the evacuation, but she did not know why.
However, they were allowing patrons to return around 10pm.
"We're hoping Shapeshifter can then start their set."
About 6000 concert-goers were affected.
The evacuation began at 9.21pm, just before the minute's silence in honour of the victims of the Christchurch terror attacks was about to begin.
Four other stages were unaffected and had observed their minute's silence before the music continued, Wright said.
Shapeshifter, the main act, was due to go on at 9.30pm.
A photo on social media showed people outside the venue, and those attending were tweeting about having to leave.
Around 20,000 people were expected to attend the show which is being held across five stages on the Wellington waterfront.
Other major events, including Pasifika in Auckland, were cancelled after the Christchurch terror attack. But the organisers of Homegrown decided to go ahead with the show.
After the Christchurch terror attack, police appealed for the public to be vigilant and report anything suspicious.
Experts warned the country would be on edge for some time.
Significant events like the Christchurch mosque shooting triggered a range of psychological effects including "hyper vigilance".
It is a condition which has our senses enter an enhanced state of sensitivity. People become more highly attuned to their surroundings, find they constantly scan the environment and absorb and process information for anything which signals danger.
Dr Ian de Terte, a senior lecturer in clinical psychology at Massey University's School of Psychology said people can also feed compelled to be more attuned because they feel it is their responsibility to do so.
"There is that heightened awareness of what's happening. The connection between cues."
De Terte said the motivation could be "fight or flight" but he also believes it is driven by a desire to help - to somehow make a contribution.
It's not a rational choice to respond in this way. It's instinct.
"People don't make rational choices. They go back to what they think is going to make them survive."
For most, the state of hyper vigilance will recede in months.
