Senior Sergeant Luke Shadbolt said police search and rescue teams and Land Search and Rescue teams spent three days scouring the area, searching baches, buildings and nearby farms.
The Lowe Corporation rescue helicopter conducted an aerial search, which included nearby Blackhead and Pourerere beaches.
There were also shoreline searches on foot.
Mr Atem's friends from Palmerston North also mobilised through Facebook for a search effort. The 22 year-old studied at Massey University.
"I pray my bro is safe and well," his brother Atem Daniel Anyuon wrote. "May God guide you'll in the right direction."
"I wish there was more I could do," a friend from Melbourne wrote.
Mr Shadbolt said there had been no sign of Mr Atem, despite extensive searches of the area.
"At this stage, we are reviewing the situation and considering other options available to us," Mr Shadbolt said.
Police were still appealing for any sightings of Mr Atem.
He is described as tall and thin with short curly black hair and dark skin. He was wearing a grey hoodie and grey jeans and was barefoot when he left the bach.
"We would like the public, especially beach-goers and boaties, to keep an eye out for Mr Atem if they are in the area. This is a popular fishing spot, especially with commercial fishermen, so someone may see something out of the ordinary either on the beach area or at sea," Mr Shadbolt said.
Police said anyone with information about Mr Atem should contact Eastern District Police on (06) 831 0700.