British tourists were on board a train to Peru's Machu Picchu when it collided head-on with another, killing one and injuring 40.
The conductor of one of the trains was killed in the crash, according to the prosecutor's office in Cusco, the city closest to the world-renowned archaeological site.
It is currently unclear how many of the wounded were British nationals.
Video footage circulating on social media shows injured victims lying next to the tracks and two damaged locomotives with broken windows and dented sides standing idle.
Credit: X/Social media
A spokesman for the UK Foreign Office said: "We are supporting a number of British nationals involved in a train collision near Machu Picchu, Peru, and are in contact with the local authorities."
A dozen ambulances and medical personnel went to the remote site, which does not have direct road access.
Police wearing hard hats and rose-coloured jackets carried injured passengers on stretchers from the trains to receive treatment.
Machu Picchu is located in south-eastPeru, where the Andes mountains meet the Amazon basin.
The 15th-century Inca citadel is the backbone of Peru's tourism industry, attracting well over 1.5 million visitors each year, averaging at 4,500 a day. The ancient site was used by the Inca empire as a royal retreat and sacred religious sanctuary.
Most visitors take a train from the nearby town of Aguas Calientes to the Unesco World Heritage site. Machu Picchu can also be reached on foot via a four-day hike.
Rail agency Ferrocarril Transandino said a train operated by PeruRail collided with another belonging to Inca Rail around lunchtime on the single track that links the town with Machu Picchu.
The cause of the accident is not yet known.
In September, about 1,400 tourists were evacuated from the Aguas Calientes train station that servesMachu Picchuand 900 others were left stranded after protesters blocked the railway tracks with logs and rocks.
Locals were demanding a new bus company be chosen in a fair bidding process to ferry visitors to the foot of Machu Picchu, and have repeatedly protested to press their demands.
The Inca empire's ancient capital Machu Picchu was built in the 15th century at an altitude of 2,500m (about 8,200ft) on orders from the Inca ruler Pachacutec.
It is considered a marvel of architecture and engineering.
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