Rubbish, a mattress and some pallets were lit on fire under the Hairini Bridge this morning.
A police media spokeswoman said the fire was producing "a lot of black smoke and flames".
She said the police were not required to attend.
A Fire and Emergency New Zealand spokesman said the fire service arrived at the scene at 11.27am.
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He said it appeared someone had been living under the bridge, with a mattress, rubbish and some pallets lit on fire.
He said no one was hurt or seen near the fire.