ACC senior media adviser Stephanie Melville said the Whangarei office would reopen today after a bomb threat was made during a phone conversation yesterday morning.
"The branch was closed to the public and police were informed. Our 50 staff also left the premises temporarily and resumed work at 1pm," Ms Melville said.
She confirmed an additional security officer would be placed outside the building.
"Following the Winz tragedy in Ashburton earlier this month, ACC has had a security officer at each of its sites."
Meanwhile, the Ministry of Social Development refused to comment about an incident at its Work and Income office in Whangarei yesterday.
A ministry spokeswoman referred media to police.
On Wednesday, Work and Income deputy chief executive Debbie Power said the department was "taking seriously" a number of threats made against staff around the country since the Ashburton shooting on September 1, when two staff were killed and another injured.
Ms Power was responding to an incident at Kawakawa on Wednesday, where a client of Work and Income called the local office threatening to blow it up. Police arrested a man in Opua.
Brendon Graham Mcnamara, 54, appeared in the Kaikohe District Court yesterday, charged with two counts of threatening to injure a Work and Income employee in relation to a bomb threat at Kawakawa. He was remanded on bail to reappear on October 7.
Court documents gave his profession as contractor and his address as no fixed abode.
Soon after midday yesterday, clients at Whangarei Work and Income reported a police and enhanced security presence, and rumours of a bomb scare.
