Specialist geolocating equipment has been deployed by Greek police searching for a missing British woman on the island of Ikaria.
Natalie Christopher, a 35-year-old astrophysicist, arrived for a holiday with her boyfriend on Saturday and has not been seen since failing to return home from a run on Monday.
Police officers, firefighters, the coastguard and volunteers have all been involved in looking for her, and they have now been joined by a new unit boasting top-of-the-line gear as the search is stepped up.
They arrived via military helicopter to lend their assistance, with the operation focused on rugged areas.
Police have already been using another helicopter with thermal cameras, according to the Cyprus Mail, but there have so far been no sightings of the scientist.
She was reportedly due to leave Ikaria with her partner on Monday, bound for Cyprus where she lives.
Her boyfriend, who has not been named, is said to have phoned her after waking up to find she was not there, and she answered to say she was out jogging in the Kerame area.
Her partner reportedly called her phone again when she failed to return and there was no response, but local reports said her phone was still on after she first went missing.
Her sister, Jena Christopher, posted on Facebook: “If you have her phone number please DO NOT call her. As this will drain the battery and the police are trying to use her phone to find her location.”
Police reportedly said they were investigating samples of blood discovered on bedsheets in the hotel room the couple had rented in Kerame.
Hotel owner Theodoris Theodorakis was quoted in local media as describing the droplets as “typical of a nosebleed”, but police said the linen had also been sent to a laboratory for DNA testing.
Local media reports said a radio signal from the phone was picked up by a cell tower on Fourni island opposite Ikaria, but authorities believe it was due to interference.
Greek media said authorities were considering switching off the tower to get a clearer idea of the location of the phone.
Members of the public are being asked to come forward with any useful information they might have, with a missing persons alert having been issued.
Authorities say they are keeping all lines of inquiry open.