UPDATE 7.52AM: A 29-year-old man is facing charged following a brawl which left two people dead and other badly injured.

A homicide investigation was launched over the weekend following a 21st party in Tairawhiti.

In a statement released this morning, police say a 29-year-old man is due in Gisborne District Court today.

"He faces a charge of wounding with intent to cause grievous bodily harm," says a police spokesperson.

"The homicide investigation continues today with Police continuing to make inquiries and provide reassurance in the local area.

"Further updates will be provided when we are in a position to do so."

EARLIER:

Additional staff from around the Tairawhiti area have been called to the region to boost Police presence in and around Gisborne following a 21st birthday party on Saturday night that ended with two people dead.

Police have launched a homicide investigation into the two deaths believed to have been caused by injuries inflicted during a large altercation that broke out from the party.

"Police staff including AOS were deployed to break up the altercation and staff attempted to resuscitate the two victims who were later declared deceased," says Acting Tairāwhiti Area Commander Inspector Darren Paki.

"Victim support is providing support for the families and welfare support for staff involved in the initial response."

Three other people were taken to hospital with injuries and they remain in hospital.

A 45-year-old man and 21-year-old man are both in a serious but stable condition with suspected stab wounds.

A 30-year-old man is in a critical condition in the intensive care unit.

"Due to the nature of this incident, Police have a presence at the emergency department of Gisborne Hospital, where access to the Emergency Department is being managed," says Inspector Paki.

"The ED remains open to those needing care."

Inspector Paki says one person has been arrested and is assisting police with enquiries.

"Our investigators are now piecing together the events leading up to the altercation, but initial indications are that the party was attended by a large number of family members, when two uninvited guests arrived.

"This is very clearly a distressing situation for the community and particularly for the families now grieving loved ones," says Inspector Paki.

"What should have been a happy occasion for this family, fueled by alcohol, has turned into an ugly and an awful tragedy for the people involved.

"Our staff will be on high alert and monitoring ongoing activity and initial indications are that the conflict did not involve rival gangs."