Ray said a search was under way at Salak mountain, about 100km south of Jakarta but "nothing has been found yet".
Hadi Tugiman, a rescue co-ordinator, said three air force aircraft and 40 rescuers from the military and police had been deployed to search for the missing aeroplane.
But he said dense jungles and mountainous terrain were hampering the search.
"The jungle is quite thick and the weather is so foggy that it's making the search difficult."
The three foreigners were from a company that sold aerial photography equipment and were on a trial flight when the aircraft disappeared, the air force said.
This is the second incident involving a Casa-212 aircraft in Indonesia this year.
A flight operated by the private Dirgantara Air Service crashed in January with three people on board.
In recent years Indonesia has seen a spate of airline accidents including an Adam Air crash that killed 102 and another involving the national carrier Garuda that killed 21 people.