In a Friday press release, Maricopa County Sheriff Joe Arpaio claimed that deputies came across suspected undocumented immigrants Thursday “in the desert during a drug interdiction operation” and called ICE on two people that they did not have enough evidence to prove were here illegally.

According to the press release, the ICE refused to take the undocumented immigrants. The sheriff says this marks the first time in recent years that Immigration and Customs Enforcement refused such a request. ICE has responded that the agency performed a routine check over the phone, and sent Border Patrol agents to take custody of the pair when the two suspects came back without prior criminal records.

Arpaio questioned the cooperation authorities will get from federal agents who will be called to verify people’s status in the enforcement of Arizona’s immigration law and be responsible for picking up illegal immigrants. Federal officials have said they’ll help if doing so conforms with their priorities, such as identifying those who threaten public safety.

The sheriff refused to say whether deputies used Arizona’s immigration law in detaining the immigrants.