HUIXTLA, Mexico—Mexican security and migration officials early on Sunday blocked the passage of a new caravan of illegal aliens, detaining several people, as the government moved to break up the group just a day after it set off from southern Mexico for the United States. At around 5 a.m. local time, members of Mexico’s National Guard and the National Institute of Migration (INM) began surrounding the illegal immigrants on the edge of the southern town of Huixtla, prompting some of them to flee, a Reuters witness said. The officials sought to intercept the ones who ran for the banks of the River Huixtla. The caravan was made up largely of Central Americans, Haitians, and some Venezuelans. The operation to stop the caravan of around 400 people comes a few days after officials dispersed another large group and followed comments by President Andres Manuel Lopez Obrador that he wanted illegal immigrants to …