PHOENIX (AP) — Arizona, Louisiana and Missouri have sued President Joe Biden’s administration to prevent federal officials from ending a public health rule that allows many asylum seekers to be turned away at the southern U.S. border.

The lawsuit was filed over the weekend in a Louisiana federal court challenging the planned May 23 end to border controls known as Title 42. The order was imposed nearly two years ago by the U.S. Centers for Disease Control and Prevention over coronavirus concerns.

The lawsuit says the order is “the only safety valve preventing this Administration’s disastrous border policies from devolving into an unmitigated chaos and catastrophe.”

It noted that several Democratic senators, including Arizona Sens. Kyrsten Sinema and Mark Kelly, have asked the Biden administration to hold off on lifting Title 42 to better prepare for an expected increase in asylum seekers.

The Department of Homeland Security has said as many as 18,000 migrants could show up daily at the southern border when the order ends. Previous rises in migration have strained law enforcement agencies and nonprofits on the border trying to provide security and shelter.

Nonprofit groups that work with asylum seekers are arguing for an end to the rule, which they say endangers people who are fleeing violence back home.

The federal lawsuit said that even though Title 42′s end is premised on a decrease of COVID-19 cases, the U.S. government has not taken other similar action such as lifting a mask mandate for airline travel.

The action also pointed to agreements Arizona and Louisiana signed with the federal government in the Trump administration’s last days about future changes to immigration policy or enforcement.

U.S. Customs and Border Protection Commissioner Chris Magnus said Monday that “we will likely face an increase in encounters above the current high levels” once Title 42 is lifted.

“There are a significant number of individuals who were unable to access the asylum system for the past two years, and who may decide that now is the time to come,” he said.

Magnus said his agency will employ additional technology, including drones and additional support personnel on the border. It will also work increasingly with other federal agencies like the Federal Emergency Management Agency and the Department of Health and Human Services, he said.

Magnus said CBP will also expand coordination with faith-based and other nonprofit groups working with asylum seekers on the border to help with short-term care and transportation.

“We are doing everything we can to prepare for this increase, ensure we continue to process people humanely, and impose consequences on those who break the law,” he said.

Republican Mayor Doug Nicolls in the border city of Yuma, Arizona. last week expressed worries the U.S. government may not be sufficiently prepared for an increase in arrivals that could overwhelm his small community.

But Democratic Sheriff David Hathaway in Santa Cruz County, Arizona, said Title 42 should be lifted because asylum seekers currently “don’t get their day in court.” The county includes Nogales, the state’s largest and busiest border crossing.