(CNN) Mexico's Foreign Ministry has asked the United States to investigate incidents in the Tijuana-San Diego border zone on Sunday that led to US Border Patrol agents firing tear gas at migrants attempting to cross the border.

In a diplomatic memo to the US Embassy in Mexico City on Monday, the Ministry of Foreign Relations requested an "exhaustive investigation" into the use of non-lethal weapons by the United States toward Mexico, the ministry said in a statement.

The ministry said Mexico is committed to protecting the human rights and security of the migrants and reiterated that tight cooperation was needed to deal with the migrant situation "with a focus on shared responsibility."

The US government has stood by its use of tear gas to disperse migrants attempting to rush the border. US Customs and Border Protection said on Sunday that some migrants were throwing rocks at Border Patrol agents, prompting the agents to respond with force to protect themselves.

President Donald Trump said on Monday that the tear gas was "very safe." He questioned why parents were approaching the border with children at all, suggesting that some of the adults "grabbed" children to better their chances of entering the US.

Read More