A man found dead yesterday after a night drinking at a Lower Hutt house had a small head injury which may have contributed to his death, say police.

The 20-year-old local man was found dead in the sleepout of a Castlerea St house, in the suburb of Wanuiomata, about 6.30am.

An autopsy was due to be carried out in Wellington today, which would help police to determine whether his death was suspicious.

Detective Senior Sergeant Ross Levy, of Lower Hutt police, said the man had been drinking with two friends in the sleepout and was found dead by a friend who lived at the house.

Neighbours told The Dominion Post they were shocked to be woken by sirens.

Laura Nanai said a lot of people came and went from the house but the residents were "pretty secluded".

Another neighbour, Hendrik Hofsteenge, said there was a "regular business" of people coming and going from the house, but never any problems.

A scene investigation was completed yesterday and Mr Levy said police were still speaking to others who were at the house on Wednesday night.