"As of yet we have no confirmation that a Swede is among them but we are in close contact with local authorities," said Sara Modin of the foreign ministry to news agency TT on Friday morning.
The chopper reportedly had left the city of Mazuco in the southeastern region of Madre de Dios late on Wednesday and set off across the Andes for the tourist hub of Cusco but never showed up at its destination.
Officials voiced hope that it had made an emergency landing in the remote Hualla Hualla region, which is at an altitude of 4,725 meters (15,500 feet), about 140 kilometers (90 miles) from Cusco.
Yashinga Tuez, a spokeswoman for the HeliCusco company that operated the flight, told AFP there were 14 people aboard, two of whom were Peruvian crew members.
"There are eight South Koreans, a Czech citizen, a Swede, a Dutch citizen and a Peruvian," Tuez said.
Earlier, Cusco police chief General Hector Dulanto said 11 South Koreans, two Austrians and a Peruvian national were on the aircraft, but Tuez confirmed there were no Austrian nationals aboard.
The interior ministry meanwhile denied reports the passengers were confirmed dead.
"No national police official has provided such information, as the search and rescue teams have not yet reached the area where the helicopter is believed to be located," it said in a statement.
A snow storm had initially hampered the search effort but a helicopter carrying a national police mountain patrol was later able to conduct an overflight of the area where the chopper may have gone down.
But amid poor weather conditions, the patrol did not see any sign of the helicopter and was forced to head back to Cusco, a police spokesman said. The search and rescue operation was eventually suspended for the night.
At the same time, two more police teams left by road for Ocongate and Marcapata, close to where the helicopter is believed to have disappeared.
A South Korean foreign ministry statement said the South Koreans were engineers and officials from four South Korean companies. They were flying toward Cusco after aerial surveillance of a possible site for a hydroelectric project near Puno in southern Peru.
"Attempts were made to reach them by mobile phones but calls were not answered. There were no automatic distress signals either, which should come from the helicopter if it crashes," the ministry statement said.
Local media said the passengers were tourists likely headed for Machu Picchu, the fabled 15th century Incan city perched on a mountain high above the town of Aguas Caliente in the Cusco region.
Hundreds of thousands of foreigners descend on the Cusco region every year to visit Machu Picchu.
A small plane crashed in February 2010 during an aerial tour of the famed Nazca Lines archeological site in southern Peru, killing the Peruvian pilot and all six tourists on board.
Five French tourists were killed in April 2008 when their plane crashed near the Nazca Lines, prompting the French government to warn visitors against flying in the country - a recommendation criticized at the time by Lima.