Immigration arrests along the U.S. southern border fell for the sixth consecutive month in November, according to statistics released Monday by U.S. Customs and Border Protection that show a significant easing of the migration pressures the Trump administration faced last spring.

The number of people U.S. authorities took into custody fell nearly 6 percent from October to November, to 42,649, the latest figures show. Arrests have dropped 70 percent since May, when U.S. authorities detained 144,116 amid a record influx of Central American families.

Mark Morgan, the acting CBP commissioner, called the change “staggering, in a very positive way.”

Morgan credited administrative changes by the Trump administration and experimental policies that tighten asylum rules and require migrants seeking humanitarian protection to wait in Mexico while their claims are adjudicated in U.S. immigration courts.

The government of Mexico also tightened its interior enforcement under the threat of tariffs from Trump, among other factors that have “all but ended” the practice of releasing families into the U.S. interior while their claims are pending in U.S. courts. The administration considers such releases into the United States as a powerful driver of illegal migration.

“Coming to our borders, illegally entering, filing false claims with a child is no longer your automatic passport into the United States,” Morgan told reporters during a briefing at CBP headquarters in Washington.

The administration’s crackdown has produced several tent camps on the Mexican side of the border, where migrant families sleep for weeks or months in squalid conditions. Mexican authorities have been slow to bring the migrants into more permanent shelters, and in recent weeks, a growing number of distressed parents have opted to send their children into the United States alone.

The November figures show a 17 percent increase in the number of unaccompanied children taken into custody from October to November, with U.S. authorities encountering 3,321 such children crossing the border.

Children arriving without a parent typically are sent to child migrant shelters until the U.S. government identifies an approved sponsor who can take custody, typically another relative.

Morgan noted that while the number of families crossing the border has declined overall, more Mexican parents and children have been taken into custody recently, in part because many of the Trump administration’s asylum restrictions cannot be applied to Mexican nationals.

When asked about a videotape released by Pro Publica last week showing the flu-related death of Guatemalan teen Carlos Gregorio Hernández Vásquez in a Border Patrol quarantine cell in May, Morgan declined to comment, citing an internal investigation.