THESSALONIKI — Greek authorities say a search and rescue operation has failed to locate a large group of migrants on an islet on the Greek side of a river that runs along the border with Turkey, which is a major crossing point for people illegally entering Europe.

A police statement Thursday said repeated efforts to locate the migrants, whose presence on an islet in the Evros River was reported by Turkish authorities, were fruitless.

An earlier police statement had said that the migrants had been located. A police spokeswoman later said that statement had been wrongly phrased, and that the information it contained had been based on what the Turkish authorities reported.

Relations between regional rivals Greece and Turkey are at a low point, and Athens routinely accuses Ankara of encouraging migrants to cross illegally into Greek territory. Turkey in turn accuses Greek authorities of illegally turning back migrants who have made it over to the Greek side, without allowing them to apply for asylum.

Last month, a group of 38 migrants was found on a Greek islet after several days of reports that they were being pushed from one side of the border to the other.