Mexico City, Mexico - Mexican President Claudia Sheinbaum said Tuesday that federal prosecutors are investigating potential violations of national security following an incident in the northern Chihuahua state that left two US government employees dead.

The circumstances of the deaths and the identity of the two Americans remain unclear.

"We're investigating what these people were doing and what agency they were working for," Sheinbaum told reporters.

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The US embassy in Mexico only identified the two victims as employees and said they had died in a car crash. Sheinbaum and Mexican officials have said the incident was bound up with the country's violent drug war.

She said the deaths indicate "that there was a joint operation" between the Chihuahua state government and US agents, meaning federal authorities "will need to consider appropriate sanctions" if US agents were acting without authorization on Mexican soil.

"Any activity that US agencies carry out on our territory" needs to adhere to Mexican national security laws with authorization from the federal government, Sheinbaum said.

The president added, however, that security collaboration between both countries has functioned smoothly. "There's communication, it works very well," she said.

Mexico has faced intensifying pressure from the Trump administration to crack down on organized crime gangs.

Though Mexican officials have coordinated operations and shared intelligence with US security agencies, Sheinbaum and her top security official have repeatedly told reporters that there are no US agents carrying out on-the-ground operations.