SAN DIEGO/NEW YORK (Reuters) - The Trump administration will increase criminal prosecutions of parents entering the United States illegally and place their children in protective custody, stepping up efforts to tighten immigration enforcement, U.S. officials said on Monday.

Attorney General Jeff Sessions and Thomas Homan, acting director of U.S. Immigration and Customs Enforcement, said the policy was not new and that the government was expanding procedures already in place. They were speaking at Friendship Park, San Diego, at the U.S.-Mexico border.

“We have always separated families under two situations, one when we can’t establish them as a parent and that child is being trafficked,” Homan said, adding that migrant smugglers sometimes pose as parents to children that are not theirs. “The second situation when we separate is when we prosecute.”

“People are dying trying to enter this country. There is a right way to do and a wrong way to do it,” Homan said, who has announced that he would retire this year.

In April, Sessions announced a “zero tolerance” policy in which illegal entrants to the United States would be prosecuted in federal court.

Previously, people apprehended crossing the border illegally were often deported without being criminally charged.

A person stopped by the border patrol and referred to a federal court to face charges is taken to jail by the U.S. Marshals Service and any of their children traveling with them are placed in government custody, with the Office of Refugee Resettlement, Sessions said.

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“If we do our duty to prosecute most cases, then children inevitably for a period of time might be held,” Sessions said, speaking over shouts from a protestor with a bull-horn and mariachi music played by a band on the Mexico side.

Reuters first reported the government’s idea to separate parents and children apprehended at the border in March 2017.

In April, the administration said it was no longer considering such action because of a decline in apprehensions of families at the U.S. border with Mexico.

Apprehensions have now risen to levels seen during the administration of former President Barack Obama, frustrating President Donald Trump, who has made illegal immigration a focal point of his administration.

“Illegal immigration must end!” Trump tweeted on Friday.

Immigration advocates have said that separations of children from parents have been happening for months. The American Civil Liberties Union filed a lawsuit in February to challenge the practice.

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An official with the Department of Homeland Security (DHS), speaking on condition of anonymity, said on Monday that the agency had signed onto the policy on Friday.

Families seeking asylum should turn themselves into authorities so their petitions can be processed instead of attempting to cross illegally, the official said.

The DHS said on Monday that there had been about 30,000 prosecution referrals since the start of the 2018 fiscal year in October, up from 18,642 prosecutions for the entire 2017 fiscal year.

Sessions was scheduled to speak earlier on Monday in Arizona. In prepared remarks, he said the United States would also prosecute immigrants who pay smugglers to bring children across the border.