Poisonous fumes from an Indonesian volcano killed six school children who were camping on the mountain and sickened several others, a doctor said Sunday.

The incident happened Saturday close to one of the two craters on Salak Volcano, which lies just south of the Indonesian capital, Jakarta, said Jusuf Fauzan, a doctor at a hospital in the nearby town of Bogor.

He said families of the victims had refused permission to perform autopsies, but the dead were believed to have been poisoned by gases from the crater. The six were found with blood and foam on their mouths and noses, he said.

The victims, who were between the ages of 14 and 16, were among about 50 students spending the weekend on the mountain, media reports said. Their bodies were evacuated from the 7,152-foot peak on Sunday.

Indonesia has more active volcanoes than any other nation and climbing them when they are not specially active is a popular pastime. Salak is one of the most popular peaks in the country.