Authorities have declared a red alert because the Nevado del Huila volcano may be on the verge of a full-scale eruption. There have been no reports of damage or injuries.The volcano, which is in the Andes 150 miles (240km) south-west of Bogotá, erupted at about 11pm yesterday, the Colombian Institute of Geology and Mining said.Martha Calvache, a deputy director of the institute’s seismic department, told a local radio station it was not possible to estimate the size of the eruption, but the volcano was expelling ash. “Other types of material could come, like lava, but we don’t at the moment know the exact situation,” she said.At 5,364m, the glacier-capped Nevado del Huila is the highest active volcano in Colombia. It lies in the centre of a national park that attracts thousands of climbers and walkers every year, and is close to Colombia’s largest river, the Magdalena.It had been dormant for more than 500 years until showing heavy activity last year.Since February 2007 there have been more than 7,000 seismic events, all classed as minor, and a continuous state of alert in surrounding residential areas.In April last year the volcano erupted twice, causing avalanches, mudslides and local flooding. Some 4,000 people were evacuated.The latest activity started with a series of earthquakes inside the volcano last month, when Colombian authorities immediately declared a state of yellow alert. They increased it to orange two weeks later, indicating that an eruption could be expected within days or weeks, and today lifted it to red, signalling an imminent and active eruption.