Illegal crossings began rising last year but skyrocketed in the months after President Biden took office. As CBP arrests increased this past spring, Biden described the rise as consistent with historic seasonal norms. But the busiest months came during the sweltering heat of July and August, when more than 200,000 migrants were taken into custody.

During a confirmation hearing Tuesday for Chris Magnus, the Tucson police chief Biden has nominated to lead CBP, Republican senators pressed him to characterize the surge as a “crisis.”

Magnus called it a “significant challenge,” echoing the Biden administration’s preferred term, adding that “the numbers are very high.” CBP is expected to release the 2021 fiscal year data later this week.