Mr Field said she was complaining of chest pains.
He said the serious crash unit was at the scene.
"They will be investigating if anyone was at fault."
Counties Manukau Fire Service assistant area commander Craig Monrad said the truck involved was from the Howick Station and was responding to a car accident in Whitford.
"As they approached the incident there was a car in front and the driver braked, and as a consequence the truck collected the car and pushed in through the intersection and into the traffic light on the other side of the intersection."
Mr Monrad said it was not the first time a fire truck had crashed on the way to a job, but it was not very common.
"These things happen, but it's unfortunate."
He said it was standard for the police serious crash unit to investigate any crash involving a fire truck and ensure the vehicle complied to road standards.
Police had taken the truck to inspect it, he said.
Mr Monrad said the appliance involved in the crash was the second called to the Whitford incident, with the Otara Station attending to that crash.