Washington, Jun 6 (IANS): Migrant apprehensions on the US-Mexico border soared to 132,887 in May, compared to 99,304 in April, US Customs and Border Protection (CBP) has said.

In May, 11,507 unaccompanied minors, 84,542 family units (an adult accompanied by at least one minor) and 36,838 single adults were apprehended, the CBP said in a report on Wednesday.

Apprehensions of family units, according to the CBP, surged from 58,724 in April to 84,542 in May, reports Efe news.

The number of unaccompanied minors apprehended at the border rose from 8,900 in April to 11,507 in May, while apprehensions of single adults increased from 31,680 to 36,838.

During the current federal fiscal year, which ends on September 30, a total of 593,507 migrants have been apprehended on the southern border, with family units accounting for the bulk of those apprehended at 332,981 cases.

The number of unaccompanied minors totals 56,278 so far in FY 2019, while apprehensions of single adults have reached 204,248.

Migrant arrivals spiked in May, compared to March, when 92,840 people were apprehended at the border, CBP said.

In May, 11,391 people were denied admission to the country, the federal law enforcement agency said.

The CBP report was released just days after President Donald Trump said his administration would impose escalating tariffs on Mexico unless that country took aggressive steps to stop the flow of illegal migrants from Central America.

On May 30, Trump said that he would slap a 5 per cent tariff starting June 10 on all Mexican imports unless the neighbouring country halted the northward flow of US-bound migrants.

Mexican President Andres Manuel Lopez Obrador said on Wednesday that he was still "optimistic" that a deal would be reached with the US to avoid the imposition of tariffs.

Trump's tariff threat threatens ratification of the US-Mexico-Canada Agreement (USMCA).

The USMCA is an updated version of the 25-year-old North American Free Trade Agreement (NAFTA) among Canada, Mexico and the US.