WASHINGTON (Reuters) - U.S. officers arrested or denied entry to over 103,000 people along the border with Mexico in March, a 35 percent increase over the prior month and more than twice as many as the same period last year, according to data released by U.S. Customs and Border Protection on Tuesday.

The steady increase in migrant arrivals, which has been building over the past several months, is driven by a growing number of children and families, especially from Central America.

Children and people traveling as families made up 67 percent of those arrested by U.S. Border Patrol agents between official ports of entry in the month of March, officials said. In March 2018, the same category made up one third of arrests.

U.S. President Donald Trump has grown increasingly frustrated with the rising number of Central American migrants attempting to cross the southern border, and his ire has been directed at his own officials, Congress, and Latin American countries, who he says have not done enough to stop their citizens from traveling to the United States.

On Sunday, Trump’s top homeland security official, Kirstjen Nielsen, said she was stepping down, and a senior administration official said other agency leaders had not done enough to crack down on the surge in immigration.

Immigration experts believe more migrants are likely to attempt to cross in the coming months, as numbers typically peak around May.