The number of migrants attempting to cross illegally into the United States remained high in May, according to administration officials and Border Patrol agents, an early indication that “zero tolerance” measures separating parents from their children and President Trump’s deployment of National Guard troops have not had an immediate deterrent effect.

The Department of Homeland Security is expected to publish its closely watched monthly arrest totals in coming days, and Trump administration officials are bracing for a new eruption from the president. He has treated the statistics as a gauge for the success of his hard-line immigration policies, and when border arrests fell to historic lows in the months after his inauguration last year, Trump touted the decrease as a personal triumph.

Since then, migration trends have reversed. In March and again in April, border arrests exceeded 50,000, the highest monthly totals of Trump’s presidency, sending him into fits of rage, aides say. Trump unloaded on DHS Secretary Kirstjen Nielsen during a Cabinet meeting May 9, scorching her for nearly 30 minutes over the spike in illegal crossings while demanding she “close” the border.