Detective Inspector Greg Murton yesterday said Lomax's death was clearly a homicide but he would not comment on his injuries or if a weapon was involved.
A post-mortem examination will be held tomorrow.
One friend described him on his Facebook page as a "hearty solid young man" who will be missed, and another said he was a "hard young bugger".
Another said: "This breaks my heart R.I.P my homie you always had my back."
The area where the body was found has been under police guard and a forensic examination would take place over the next few days, Murton said.
The cordon at Harrs Rd is in an isolated area surrounded by farmland and lifestyle blocks, just off South Eyre Rd, Swannanoa.
One resident said the body of Marie Davis, 15, was found in a similar part of the Waimakariri River 11 days after she went missing in April 2008.
The resident said police searched the riverbank and the area around her house then. In that instance she and her husband had heard a car racing up the road late at night.
This time they had been watching the election debate and had not heard anything, she said.
"You just feel very sad for all the people who are touched by such a tragedy. It's just horrid to hear of these tragedies."
She said the area was usually pretty safe although she would not walk along the river on her own because she said criminals were known to grow cannabis there.
Another resident said he went for a walk down the road about 5pm yesterday and didn't notice anything unusual.
Police would like to hear from anybody who was near Harrs Rd and South Eyre Rd yesterday between 8pm and 10.30pm.
Anyone with information can phone Christchurch Police on (03) 363 7400 or Crimestoppers anonymously on 0800 555 111.
