A rescue operation was launched in the Samaria gorge on Crete yesterday for two Polish tourists that have been missing since Saturday, authorities said.

The two tourists, a 40-year-old woman and her 34-year-old brother, had taken part in a hike through the gorge on Saturday but failed to appear at a prearranged meeting point later in the day.

Attempts by trip organizers to contact the pair by mobile phone failed, prompting them to notify authorities.

It was not clear why authorities had not been immediately contacted.

An airplane joined a large ground force that combed the area with the help of sniffer dogs and volunteers.

The gorge, which is located in the Hania region, is the second longest in Europe and can take between four and seven hours to walk through.