ARGENTINE police have detained four more people over the rape and murder of two French tourists.

The last young backpackers flew away from Machu Picchu as clouds closed in again, leaving Peru to grapple with flood damage that will close its top tourist site for weeks, or perhaps months.

Heavy rains and mudslides in Peru blocked the train route to the ancient Inca citadel of Machu Picchu, keeping nearly 2,000 tourists stranded.