OKLAHOMA CITY -- The Trump administration no longer needs to detain migrant children at an Oklahoma Army base and preparations to house them there have stopped, the U.S. Department of Health and Human Services said in a statement.

"Over the last several weeks HHS has experienced a decrease in Department of Homeland Security referrals of unaccompanied alien children (UAC). Additionally, HHS has been placing UAC with sponsors at a historically high rate. As such, the UAC Program does not have an immediate need to place children in (holding) facilities," said Evelyn Stauffer, spokeswoman for the agency's Administration for Children and Families.

Stauffer, who did not immediately reply to messages seeking further information, said no children have been held at the base at Lawton, about 80 miles (130 kilometres) southwest of Oklahoma City.

Homeland Security officials said earlier this month there was a 28% drop in the number of migrants encountered by Customs and Border Protection in June, amid a crackdown on migrants by Mexico.

There were 104,344 migrants in June, down from 144,278 the month before. Homeland Security officials said the numbers of single adults, families and unaccompanied minors at the border had all declined.

Dream Action Oklahoma, which helped organize a rally and march of an estimated 400 people to Fort Sill last weekend to protest plans to use the base, said they were pleased by the announcement.

"The organizing coalition is continuing the resistance of child imprisonment in Oklahoma," the group said in a statement.

Japanese Americans and Native Americans were among those who took part in last weekend's march and rally in front of one of the entrances to Fort Sill, where hundreds of Japanese and Japanese American people were detained by the federal government during World War II. Fort Sill also housed migrant children in 2014 under the Obama administration and was used to hold Apache prisoners of war from 1894-1910.

Donelle Harder, a spokeswoman for Oklahoma Gov. Kevin Stitt, said the White House notified Stitt of the change of plans Friday, but said the base could still be used for temporary housing in the future.

"They will maintain the infrastructure in case a need arises, in case of any emergency," in which the number of children coming into the U.S. increases, such as flooding or earthquakes in other countries, Harder said.