Ian Robertson, 59, disappeared north of Cooktown about four days ago, police said on Tuesday.

His black Ford Falcon ute was found parked near Battle Camp Road near Hope Vale on Monday.

"Concerns are held for his safety because we can't determine any known cause as to why his vehicle should be located in that remote area," Senior Sergeant Ed Lukin told reporters.

"There's no indication of where he has gone."

Snr Sgt Lukin said it was unlikely Mr Robertson had been taken by a saltwater crocodile or met with foul play.

He was last seen by a passing station owner taking his swag out of his ute days earlier.

"We're hoping he has got a lift with someone, however, the circumstances of his disappearance have led us to believe he is in the area and needs assistance urgently," Snr Sgt Lukin said.

Police and State Emergency Service personnel have started a ground search of the area near to where Mr Robertson's car was found.

"Conditions are very difficult. It's hot, humid and the bush is very thick and dense," Snr Sgt Lukin said.

"It's quite green and lush at the moment. The grass is quite high. The dense foliage makes it difficult for searchers to penetrate.

"If (Mr Robertson) has had a medical episode and has fallen into the grass he could be quite difficult to spot from even a short distance."

Snr Sgt Lukin said Queensland Government Air's Rescue 510 helicopter crew used night-vision goggles to search for Mr Robertson on Monday but "came up empty-handed".

Mr Robertson is about 170cm tall with dark brown hair and brown eyes.

Australian Associated Press