Mexico formally requested that US state attorneys general criminally investigate cases of immigrants who have died in Immigration and Customs Enforcement custody or during raids, the Mexican government said Tuesday.

The request follows the death of Mexican immigrant Lorenzo Salgado Araujo, who was shot and killed by an ICE agent in Houston. Since the beginning of Donald Trump’s second term, 17 Mexican immigrants have died during immigration enforcement, 14 in ICE custody and three in agency operations.

Mexico’s foreign ministry had previously said it would make the request , which was formalized on Tuesday, according to the ministry. It said a similar request will also be sent to the US Department of Justice.

The United States is not legally obliged to act on the requests.

Also, the Mexican government said it had started sending letters to US detention centers where Mexican immigrants had died, demanding they “immediately cease the actions or omissions that resulted in these deaths, such as preventing access to prompt and expedited medical care, as well as the application of policies incompatible with medical and penitentiary standards”.

The first center to receive the letter was Adelanto, in California, where four Mexican immigrants died.

The letters are a first step toward “the eventual filing of civil lawsuits” against the companies that operate the detention centers to stop human rights violations, according to the ministry.

Last week, Roberto Velasco, the Mexican foreign minister, said his country would go directly to US authorities to request criminal investigations in cases of Mexicans killed in ICE custody or enforcement operations.

Salgado Araujo, who had no criminal record and had lived in the US for 35 years, was shot last Tuesday while driving his construction crew to a job site in Houston. His death sparked protests in Houston and demands for an independent investigation from Democrats and Salgado Araujo’s family.

The Department of Homeland Security, which oversees ICE, said the 52-year-old had rammed an ICE vehicle, and that a federal agent fired a weapon in self-defense.

Velasco also sent a letter to Volker Türk, the UN high commissioner for human rights, requesting that US authorities gather information on the deaths of the Mexican immigrants in ICE custody and analyze the “compatibility of these events with international human rights obligations”.

The foreign minister also asked Türk to seek the opinion of the Human Rights Council, a UN intergovernmental body that promotes human rights, on the cases and offer recommendations.

The developments mark an escalation in Claudia Sheinbaum’s response to Trump’s immigration crackdown. The Mexican president earlier this year ordered Mexico’s diplomatic missions across the US to regularly check in with ICE detainees, and her government even lodged a complaint with Türk.