A volcanic eruption has eased enough to allow a local airport to open, but thousands of people are staying clear of Colombia's most active volcano as more activity is feared, authorities warned Sunday.

Ashes are still falling near the Galeras vocano in the south, after Friday's eruption, but a color-coded alert has been lowered from red to orange, the Colombia Institute of Geology and Mining (Ingeominas) said.

An orange alert means a new eruption was possible "in days or weeks," rather than imminently, it added.

Friday's eruption caused no casualties, but some 1,000 people were evacuated from around the volcano to Pasto, the capital of Narino department. Another 8,000 people defied evacuation orders, refusing to leave their homes.

Authorities are urging people living in the Galeras foothills to leave for Pasto, 920 kilometers (570 miles) south of Bogota, as the danger of new eruptions is still quite high, warned Ingeominas deputy director Martha Calvache.

Regional authorities said traffic restrictions are being maintained on a highway linking Pasto to villages close to Galeras, but Antonio Narino airport serving Pasto has been reopened for business.

A 1993 eruption of Galeras, which rises in the Andes mountain chain to an altitude of 4,270 meters (14,029 feet), killed nine people, including six scientists who had gone down into its crater to take gas samples.

Ingeominas says the volcano rumbled back into action again in 2004 and has been causing about 19 earthquakes per year.

The institute said an orange alert also continued for areas near the Huila volcano, where sizeable volcanic activity also has been detected in recent weeks.

Huila, at some 5,363 meters (17,595 feet), last erupted in November 2008, killing 10 people.