Claudia Sheinbaum, Mexico’s president, said on Monday that her government told the United States, in a diplomatic note, that the unauthorized presence of US officials at an anti-narcotics operation in the northern state of Chihuahua should not be repeated.

The incident came to light after two US officials, along with two Mexican officials, were killed in a car crash on 19 April after the operation. Sheinbaum has said the federal government was not aware of the participation of the US officials, who were widely reported to be CIA officers.

“What we told [the US] was that the federal government didn’t know about the involvement of these people [in the operation] and we hope that it’s an exception,” Sheinbaum said in her daily morning press conference.

Mexico requested that “from now on, as has been done, our constitution and national security law should be followed”, Sheinbaum added, saying that the US had indicated its agreement.

On Saturday, Mexico’s security cabinet said in a statement that the US officials lacked formal accreditation to participate in security activities in Mexico and that one of them had entered the country as a tourist.

The deaths of the two Americans rekindled US-Mexico tensions over security cooperation. The presence of US personnel in anti-cartel operations is a deeply sensitive matter in Mexico.

Sheinbaum has long maintained that she welcomes intelligence sharing and security cooperation but will not accept US agents or forces participating in operations on Mexican territory.

In contrast, Donald Trump has repeatedly called for greater use of US military force to combat Mexican cartels, and has threatened that the US could go it alone if Washington feels Mexico isn’t doing enough.