Paris:
More than 7,000 migrants have been arrested in Calais trying to illegally cross the Channel into Britain in the first half of 2014, more than double the figure a year ago, officials said on Friday.
The prefecture of the French port town said 7,414 people had been arrested between January and June this year against 3,129 a year earlier.
"We have noted that there are considerably more illegal migrants, and during our checks we find more," a source at Calais port told AFP.
In the first two weeks of July alone, some 1,200 people were arrested but most of them were released because the detention centres are already overcrowded.
French police have been trying for years to dislodge migrant camps in and around Calais.
But the flow has been persistent, with many migrants hoping to hide in trucks or other vehicles crossing to Britain, where they believe conditions are better for would-be refugees than in France.
Most of the immigrants come from the Horn of Africa, especially from Sudan, Somalia and Eritrea, a source close to the case said.
"They arrive in Lampedusa (Italy's southernmost tip) and come to France by train or bus and get to Calais," the source said.
At the three points where there are Channel crossings -- Calais, Dunkirk and the Channel Tunnel -- 10,500 migrants were arrested in the first half of 2014, against 5,133 a year earlier.