At least 18 people died after being trapped in an illegal gold mine that collapsed in Indonesia's West Kalimantan province, a search and rescue agency official said on Sunday, as efforts continued to search for possible survivors.

Small-scale and illegal mining is a flash point for conflicts and accidents in Indonesia, where mineral resources are often situated in remote and protected forest areas that are difficult for the government to regulate.

The collapse occurred on Saturday at 11 a.m. but the rescue agency was not notified until evening, Leonardus Sabar Umbara, officer in charge at the West Kalimantan rescue headquarters in Pontianak, told Reuters.

A rescue team reached the site late on Saturday and found 18 victims, 16 men and two women. Fifteen have been identified. "Local people are reluctant to report incidents like this as many of them are engaged in illegal mining," Umbara said.

People in the area were not sure how many other miners may have been trapped, but television station Metro TV said there were up to 500 workers at the site on Saturday.

A similar collapse in the same area killed nine people several years ago, Umbara said.