Mexico has asked the United States to investigate an incident in which US agents fired tear gas to stop migrants who attempted to breach the border fence at Tijuana on January 1. <br />''<br />''Mexico's foreign affairs ministry said, it sent a diplomatic note to the United States Embassy about the incident. In a statement issued yesterday, the Mexican foreign ministry said it lamented any violent act along its border. <br />''<br />''<br />''<span style="color: #222222;"> US Customs and Border Protection agency said that agents fired tear gas after migrants threw stones. </span><br />