MEXICO CITY (AP) — Mexico’s government said Saturday that two U.S. federal agents recently killed in a car crash in the country’s northern region were not authorized to participate in operations in Mexico.

The role of the two CIA agents who were returning from destroying a clandestine drug lab in the northern Mexican state of Chihuahua remains unclear.

Local government officials have said they were part of a convoy when their car drove off a ravine last weekend and the vehicle exploded. Two Mexican officers also were killed.

The Americans killed were from the CIA, The Associated Press confirmed earlier this week with a U.S. official and two other people familiar with the matter who spoke on the condition of anonymity to discuss sensitive intelligence matters.

The CIA has declined to comment.

A statement from Mexico’s Ministry of Security said one U.S. agent entered Mexico as a visitor while the other entered with a diplomatic passport.

It also asserted that Mexico’s government was not aware of foreign agents operating or planning to participate in an operation on its soil.

The ministry said it is reviewing the case with local authorities and the U.S. Embassy in Mexico.

“Mexican law is clear: it does not permit the participation of foreign agents in operations within the national territory,” the ministry said in a statement.

It added: “The Government of Mexico reiterates its willingness to maintain a close, serious, and respectful relationship with the Government of the United States for the benefit of the security of both countries.”

Officials from both countries have offered contradictory accounts on the issue, with Mexican President Claudia Sheinbaum admitting on Wednesday that federal forces were involved after Mexico’s government said it had no knowledge of any operation or U.S. involvement.