(CNN) US Border Patrol apprehensions along the southern border dropped in June for the first month since January, according to preliminary internal data obtained by CNN.

There were nearly 95,000 apprehensions on the US-Mexico border last month, down about 28% from 132,887 in May -- the highest month in more than a decade. Despite the drop, this June was much higher than the same time last year, when there were 34,089 apprehensions.

The numbers are in line with forecasts from acting Homeland Security Secretary Kevin McAleenan, who said Friday that it appeared there would be a 25% decrease in June numbers of migrants crossing at the US-Mexico border.

A dip in border crossings is common during the hot summer months, though McAleenan downplayed the role of seasonal trends in migration, saying that he expects to be able to tell by late July if initiatives undertaken by the US and Mexico governments will have a sustained impact.

Customs and Border Protection does not comment on unofficial numbers, according to a spokesperson. The agency generally releases final monthly numbers towards the beginning of the subsequent month.

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