Two agents reportedly from the Central Intelligence Agency (CIA) in the United States have been killed in a car crash in the Mexican state of Chihuahua, leading to questions about their activities in the country.

On Tuesday, Mexican President Claudia Sheinbaum addressed the matter from the podium at her morning news conference.

She underscored that a probe is under way, as Mexican law requires that foreign agents receive federal authorisation to operate in the country.

US agents, in other words, cannot work directly with state-level Mexican officials without prior approval from Sheinbaum’s government. It is unclear whether that standard was followed in this incident.

Sheinbaum also acknowledged there were conflicting reports circulating in the aftermath of the crash about the nature of the agents’ presence in Mexico.

“A full investigation must be conducted by the Attorney General’s Office to determine whether the Constitution or the National Security Law was violated and to ensure that the authorities in the state of Chihuahua have access to all the accurate information,” she said.

Tensions have been high over the past year over the possibility that the US may seek to unilaterally launch ground operations in Mexico, thereby violating its sovereignty.

Since returning to the White House for a second term, US President Donald Trump has repeatedly threatened to take military action in Mexico to “eradicate” cartels and other criminal networks.

But Sheinbaum has rejected any such action as a red line not to be crossed in Mexican-US relations.

She reiterated that stance in Tuesday’s news conference, while welcoming collaborative efforts to combat crime.

“Joint ground operations are not permitted,” Sheinbaum said. “What has been agreed upon and stated very clearly with the United States government is that information is shared, and extensive work is conducted regarding joint intelligence.”

While she described her government’s relationship with the US as “excellent”, she did warn there could be consequences if a violation of Mexico’s laws were to be discovered during the course of the investigation.

“A formal diplomatic protest would indeed be issued, obviously, along with a request to ensure that such actions do not recur,” she said, adding that she has already been in contact with the US embassy.

For his part, US Ambassador Ronald Johnson expressed his condolences in a social media post after the crash.

“This tragedy is a solemn reminder of the risks faced by those Mexican and U.S. officials who are dedicated to protecting our communities,” Johnson wrote.

“It strengthens our resolve to continue their mission and advance our shared commitment to security and justice, to protect our people.”

It is unclear if and to what degree US agents were involved in unsanctioned ground operations in Mexico.

The Washington Post, which broke the story, initially indicated that the two agents were engaged in a counternarcotics operation, citing anonymous officials familiar with the matter.

Their car appears to have veered off the road and crashed in a ravine early on Sunday. The identities of the two US officials have yet to be confirmed.

Johnson described the two officials as “embassy personnel”. Media reports, however, have indicated they may have been members of the CIA.

Contradictory statements from authorities in Chihuahua also compounded the confusion about who was involved in the antidrug operation.

On Monday, the state attorney general’s office in Chihuahua issued a statement to insist that “only elements of the State Investigation Agency (AEI) and the Mexican army participated” in the sting.

Chihuahua’s Attorney General Cesar Jauregui Moreno has ruled out “the intervention of foreign elements”, the statement added.

According to state authorities, “instructors from the United States” were in Chihuahua “for other purposes, such as teaching how to handle drones”.

Separately, 40 officers from Chihuahua’s AEI and 40 from Mexico’s Secretariat of National Defence led a two-day operation that resulted in the discovery and seizure of a drug lab in the community of El Pinal, the attorney general’s office said.

The office insists that the Mexican law enforcement agents were simply giving their US counterparts a lift to the airport, nothing more, when the early-morning car crash occurred. The two US officials were expected to catch a flight on Sunday from the city of Chihuahua.

“We are very respectful of the sovereignty of this country and of the non-intervention of agents of any kind that are not nationals, directly in this type of operation,” Jauregui Moreno said in the statement.

Since Trump began his second term, the question of whether he might pursue policies that violate Mexican sovereignty has loomed over cross-border relations.

Last year, he labelled several Mexican cartels “foreign terrorist organisations”, seeming to tee up possible military action.

Privately, in a notice to Congress, Trump has described cartels and other criminal networks as “unlawful combatants” engaged in an “armed conflict” with the US.

To that end, he has carried out a campaign to bomb alleged drug-smuggling boats in the Caribbean Sea and eastern Pacific Ocean, killing at least 180 people.

He has also twice attacked Venezuela — once in December and a second time in early January — culminating in the abduction and imprisonment of the country’s then-leader, President Nicolas Maduro.

Trump and his officials have described the January 3 attack as a law enforcement operation. Maduro and his wife Cilia Flores currently await trial on drug trafficking and weapons charges in New York.

Legal experts, however, have described the attack as a violation of international law.

Shortly after Maduro’s removal, Trump renewed his threats that other countries could likewise face attacks on their soil. Mexico was among the targets he floated.

“We are going to start now hitting land with regard to the cartels. The cartels are running Mexico,” he told Fox News in January. “It’s very sad to watch.”

Sheinbaum has rejected that assertion, while increasing her government’s anti-cartel operations.

In February, for instance, the Mexican military led a high-profile operation that resulted in the shooting death of Nemesio Ruben Oseguera Cervantes, known as “El Mencho”, the leader of the Jalisco New Generation Cartel.