Police advised the public to avoid State Highway 2, near Te Hauke, following a large tangi for a senior Mongrel Mob member.
Hundreds of gang members joined the procession on Tuesday afternoon after a service was held at Te Kura Kaupapa Maori o Ngati Kahungunu ki Heretaunga.
Police said there was congestion on SH2 due to a large gang tangi taking place south of Pakipaki.
"Police are monitoring the tangi, and we are managing traffic to ensure everyone using the roads is safe," a spokeswoman said.
At 3.45pm, police asked motorists to avoid or delay travel on SH2 near Te Hauke for a couple hours, and for everyone on the roads to "stay patient" as the congestion is managed.
"Police are monitoring behaviour and will follow up with offences detected," the spokeswoman added.
No arrests had been made by 5.30pm.
Police also thanked the public for their patience and understanding.
Police were at 3pm called to a crash on SH2, near Horonui Rd.
Nobody was injured, but one of the vehicles is reported to have fled the scene prior to police arrival.
A police spokeswoman said there is nothing to indicate any of those involved were related to the Mongrel Mob procession.
Police also urged anyone with concerns or information about suspicious or unsafe activity to contact call 111 or 105 to report it.