Human remains have been found in the 4.3-metre crocodile responsible for taking a grandmother in far north Queensland last week.

Anne Cameron, 79, disappeared from aged care facility Ozcare near Port Douglas on Tuesday last week after she went for a walk.

On Thursday, police and SES crews made a grisly discovery of human remains, jewellery and Ms Cameron's walking stick on the banks of a creek inlet near the Mowbray River, north of Cairns.

Wildlife officers found and killed a crocodile in the Mowbray River system around 1am yesterday.

Human remains and a number of items which belonged to Ms Cameron were found in the animal, which has been euthanased.

Acting Inspector Ed Lukin described the investigation as "very protracted and difficult".

"The environment is difficult, the conditions in which EHP staff were working, the river system there, the heat of the day for the SES, they've done an incredible job," he said.

Environment and heritage protection officers trying to catch the crocodile with a floating trap yesterday. ( Supplied: Department of Environment and Heritage Protection )

"It's very emotional for all of those members that are working on these investigations and it's always difficult when we have a missing person."

Croc's bold behaviour indicated it was responsible

Chris Artiemiew from the Department of Environment and Heritage Protection said wildlife officers had been tracking the crocodile since Sunday afternoon.

"It had subtle behaviour differences which highlighted to us that it was the target animal," Mr Artiemiew said.

He said rainy weather made the job more difficult.

"It was a really big job for our wildlife officers in extenuating circumstances," he said.

"In most cases we could only target the animal in low tides, so it was a very narrow window either side."

The department does not believe the crocodile had been living in the area, as it was unfamiliar to wildlife officers working in Port Douglas.

Environment Minister Steven Miles thanked the wildlife officers for capturing the animal.

"It has been a very difficult and harrowing week for all involved, and my thoughts are with the family of Anne Cameron at this sad time," Mr Miles said.

Police are preparing a report for the coroner.