Chilean authorities evacuated thousands of people on Tuesday after one of South America's most active volcanoes erupted in the south of the country, the Associated Press reported.

The National Emergency Office said the Villarrica volcano erupted around 3 a.m. local time, sparking concerns that melting snow could trigger mudslides, which in turn could endanger nearby communities.

The 9,000-foot mountain sits in the country's central valley, 400 miles south of Santiago, Chile's capital. The nearest city, Pucón, has a population of about 22,000 people.

By Tuesday afternoon, the majority of the about 4,000 evacuees had been permitted to return to their homes, El Mercurio, Chile's paper-of-record, noted; fewer than 400 individuals were still awaiting word from the National Emergency Office.

Villarrica's volcanic activity had diminished in the afternoon hours, a development that also allowed authorities to reopen mountain roads that had been closed earlier as a precaution.

In the morning hours, local media had shown images of the volcano bursting at the top, "glowing in the dark amid heavy smoke and rivers of lava," the AP noted. Travis Armstrong, an Australian tourist who spoke with the news service from Pucón, called the eruption "the most amazing thing I've ever seen."

"It was spewing lava and ash hundreds of meters into the air," Armstrong said. "Lightning was striking down at the volcano from the ash cloud that formed from the eruption."

Rodrigo Álvarez, the director of Chile's National Service of Geology and Mining, asked residents and tourists visiting the area to be prudent and careful.

"This is not a fireworks show," he warned.

Official prohibitions to stay away from the volcano, which had last its last major eruption in 1984, needed to be followed, Álvarez added.

National Emergency Office Director Ricardo Toro told El Mercurio that according to data from the National Geology and Mining Service, Villarrica's seismicity levels have been decreasing.

"(The eruptive activity) had not reappeared, and there only a few gas emissions," he detailed.

Nevertheless, the agency is continuing to enforce a 10-kilometer exclusion zone around the volcano, Toro said. The red alert the National Emergency Office had issued overnight also remained in place, its director added.