The death of US officials following an operation to dismantle a drug lab in northern Mexico is escalating tensions with Washington, as President Claudia Sheinbaum insists her government was unaware of their involvement.At a news conference, Sheinbaum said Mexican security officials involved in the operation were never told about the presence of foreigners, which she described as a clear breach of security protocols. A person familiar with the matter confirmed that the two US nationals worked...