The authorities in Peru have declared a state of emergency around a volcano that has begun spitting ash and smoke after almost 40 years of inactivity.
The Ubinas volcano in southern Peru started erupting three weeks ago, killing livestock and polluting water.
The army has now been brought in to help evacuate nearby villages, although some residents are reluctant to leave.
Peru's Institute of Geophysics has warned that a dome of incandescent lava seems to be building up in the crater.
The volcano has been spewing out acid-laden ash and smoke over a radius of six kilometres (3.5 miles), causing eye and breathing problems for local people.
A regional official said muffled explosions were coming from the volcano and pieces of red-hot lava were expanding inside the crater.
Teams of geologists and doctors have been sent to the area to monitor the volcano and the health risks.
"It's dangerous...all the signs are that a dome of incandescent lava is building," Leonidas Ocola of Peru's Geophysics Institute told the French news agency AFP.
More than 200 people have already been forced from their homes, and several thousand more are at risk, officials said.
Around 40 families have been told to leave the town of Querapi, which lies just four km (2.5 miles) from the volcano.
Molten lava is visible inside the crater of the volcano
"Some people do not want to leave because they do not want to abandon their homes, their farms and their animals," the vice-president of the Moquegua region, Alberto Portugal, told AFP.
Some evacuees arrived on Friday and Saturday in Arequipa, the city closest to Querapi, a difficult six-hour bus ride, Reuters reported.
The ministers of health and agriculture were expected to visit Ubinas on Sunday, taking food, tents, masks and veterinary medication for animals that have been harmed from breathing toxic gas.