The number of migrants taken into custody along the U.S.-Mexico border has started to plateau after several straight months of decline, according to border enforcement statistics released Thursday by U.S. Customs and Border Protection.

The number of people apprehended or deemed “inadmissible” by U.S. border authorities along the southern border fell to 40,620 last month, down 72 percent from May, when the Trump administration declared it was at the height of a border crisis.

December marked the seventh straight month of decline in border crossings, but the month-to-month differences have shrunk significantly since September. Border enforcement actions last month were roughly on par with December 2017.

Although border crossings are leveling off, CBP said drug seizures along the border have continued to rise, with overall drug interceptions nationwide up 28 percent from this time last year. There has been a particular jump in fentanyl seizures, which have risen 80 percent.

The Trump administration has attributed the lower number of border crossers to several initiatives that have made it more difficult for individuals and families to seek asylum in the United States. Those have included a tightening of asylum qualifications and pilot programs that have expedited deportations or forced tens of thousands of other asylum seekers to wait in Mexico while their asylum claims are adjudicated in U.S. immigration courts.

“This seven month decline is a direct result of President Trump’s network of policy initiatives and our ability to effectively enforce the law, enhance our border security posture and properly care for those in custody,” CBP acting commissioner Mark Morgan said in a statement Thursday.