It would be every backpacker’s nightmare, were it not so far-fetched. Six young Australians who went travelling in South America have found themselves at the centre of a murder inquiry, named as prime suspects in the death of a Peruvian doorman at a Lima apartment block.

The six – three from Sydney, three from Melbourne – checked into their 12th-floor holiday apartment in January 2012 following a 21-hour bus journey from Cuzco, where they had climbed Machu Picchu. Three hours later, they heard screams and a “thud”, and saw the body of the doorman, 45-year-old Lino Rodriguez Vilchez, on the footpath outside.

Police initially ruled his death a suicide, and after the Australians had been questioned, along with everyone else in the block, they were told they could continue with their travels. It was not until five months later, after they had returned home, that they learnt that the case was being treated as a murder, and they were accused of throwing Mr Rodriguez off their balcony.

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The six, who have protested their innocence, have now been ordered to return to Peru this week to make statements ahead of a trial, or be placed on an international wanted list by Interpol. Australia has an extradition treaty with Peru.

The group – Sydney-based university students Sam Smith, Harrison Geier and Andrew Pilat, and Melbourne residents Jessica Vo, her partner, Hugh Hanlon, and his younger brother, Tom, all in their 20s – say their only contact with Mr Rodriguez was when he helped them carry their luggage to the lift and, shortly afterwards, gave them directions to a grocery shop.

It was after they returned from shopping, at about 3pm, that Mr Rodriguez’s body was found. The six, who maintain he never set foot in their apartment, believe police changed tack following a public campaign by Mr Rodriguez’s brother, Wimber, who claims the doorman was beaten up and pushed off the Australians’ balcony following a row about noise.

“It’s a complete lie,” Ms Vo, who embarked on the South America trip after recovering from ovarian cancer, told Australia’s ABC TV this week. “I don’t know how they [the police] could possibly have that type of scenario in their head, because there’s no evidence.” In a separate interview, she told Fairfax newspapers: “We were in the wrong place at the wrong time.”

The two groups of friends had got to know each other in South America and began travelling together. They decided to treat themselves to a bit of comfort – the Lima apartment – after a punishing spell on the backpacker trail.

The nightmare began this time last year, three months after they returned to Australia. Mr Geier noticed that Spaniards were posting on his Facebook page; when he clicked on links, he saw articles from the Peruvian media, making clear he and his friends were suspected of murder.

Peruvian newspapers have reported that Mr Rodriguez had debts, and that his family would not receive an insurance payout if his death was a suicide.