UPDATED: 7.50PM Part of Auckland International Airport was evacuated tonight after a defective apparatus caused an alarm to go off.

Planes stopped boarding and those on the runway were grounded while emergency services investigated an incident.

The fire service and airport emergency service were at the scene, but operations are now returning to normal.

A defective apparatus caused an alarm and is being investigated. Operations are in process of returning to normal at Auckland Airport.

— Auckland Airport (@AKL_Airport) April 4, 2016

Matthew Jones was boarding a plane to Australia at the time when he heard loud gun shot like bangs and angry screams.

"I wasn't sure what to make of it but moments later we were approached by Government officials and ordered onto the runway of the airport and told to remain there til further notice.