Beachgoers were shocked by the sight of 150 gulls dying en masse in Horowhenua this weekend.
Carolyn Press-McKenzie of the Helping You Help Animals (HUHA) animal rescue charity says her staff rushed to a beach north of Otaki, but found only 15 birds still alive - which were taken to Massey University's wildlife hospital in Palmerston North.
"It's a pretty confronting sight seeing so many dead animals and some were still literally dropping out of the sky, some were dive-bombing into the ocean and drowning at sea and some were managing to get to the beach but dying quickly in front of locals."
Press-McKenzie said of the 15 gulls found alive, 10 have since died. She said it was possible the flock may have been poisoned with a pest control agent.
Post-mortems have been carried out and the results are expected early this week.