UPDATED 12:15pm: Police and fire investigators are working to determine the cause of a large fire on the Domain Road bridge construction site in Papamoa.

Emergency services were called to the bridge at 8pm yesterday.

Fire fighters spent all night at the bridge dampening down hotspots.

Police say it's too soon to say if the fire was set deliberately.

NZTA Waikato Bay of Plenty Regional Director, Harry Wilson, says they're thankful the construction site was closed at the time and no one was injured.

He says the impact on the project won't be clear until engineers can inspect the damage.