"Apparently the military was not aware that people who were not Mexican citizens were participating," Sheinbaum said at a press conference on Wednesday.
She added that this is "not something Mexicans should take lightly" and that the government is investigating whether it could be a violation of national security laws.
Two Mexican police officers also died in the crash, which occurred on Sunday when the car, along with several other vehicles, was returning from a raid on a drug laboratory in the northern border state of Chihuahua.
According to Sheinbaum, sanctions are being considered against the state government, as no representatives of US authorities can be allowed to "operate on the ground in Mexico."
Conflicting information
The involvement of the US intelligence agency, the CIA, was confirmed on Tuesday by three sources to the AP.
This was followed by a couple of days of conflicting information from the authorities about the Americans' involvement and which organization they represented. The CIA agents were initially identified as US embassy personnel.
At an early stage, local Mexican authorities confirmed cooperation with the United States, while President Sheinbaum said she was not aware of any joint drug operation.
Fine balance
The murky statements from the authorities have fueled a previous debate about the extent of US involvement in Mexico's security efforts. Sheinbaum is under pressure from US President Donald Trump to crack down harder on drug cartels. The CIA has also recently increased its cooperation with Mexican authorities, as part of efforts to stop drug trafficking.
For Sheinbaum, it's a fine balance, where she tries to maintain good ties with the United States, oppose punitive tariffs, and prevent American military involvement. Instead, she has advocated for increased intelligence cooperation.
