MEXICO CITY, June 19 (Reuters) - Mexico City schools that had just gone back to in-person classes will be closed again starting Monday as the sprawling capital climbs into a higher tier of coronavirus risk, education authorities said on Saturday. Mexico City officials had loosened restrictions on gatherings in schools, hotels, stores and restaurants just two weeks ago as the dense urban zone moved into the lowest risk tier of the government"s four-level "traffic light" model. But the federal Health Ministry on Friday evening put Mexico City, home to more than 9 million people, a step higher on the scale for June 21 to July 4. Mexico City Mayor Claudia Sheinbaum said the city"s Epidemiological Traffic Light, a calculation of risk factors, has climbed to nine points from eight points, putting the capital into the more restrictive tier. Mexico City"s Federal Educational Authority (AEFCM) said in a statement the suspension of classes applied to both private and public schools. Mexico, which began COVID-19 vaccinations at the end of 2020, has reported more than 230,959 deaths from the coronavirus and 2,471,741 confirmed infections.