GUATEMALA CITY, Aug 4 (Reuters) - Guatemala has begun to receive flights of undocumented migrants sent back from the United States under a new policy allowing fast-track expulsions for some families at the U.S.-Mexico border, Guatemalan and U.S. authorities said on Wednesday. The measure announced by U.S. officials last week, called "expedited removal," applies to families that have not sought U.S. asylum or who do not qualify, and comes as border arrests in recent months have risen to 20-year highs. A flight from Brownsville, Texas, arrived in Guatemala on Wednesday with 16 families comprising 50 people, including a number of young toddlers carried off the plane in their parents" arms. Among the passengers was Marvin Santos, 25, who had trekked to the United States with his wife and 5-year-old daughter, hoping to meet up with relatives already in the United States and pursue a better life. The journey cost him about $11,600, which he financed by selling his motorcycle and other belongings as well as taking out a bank loan, he said. Once his family crossed into the United States, they were detained. Within a week, they were tested for COVID-19 and told they would be sent back to Guatemala. "We started to cry because that was not the plan we had ... We basically have nothing here, we sold everything," Santos said in an interview shortly after stepping off the plane, as his wife cried by his side. The flights returning families to Guatemala began on Friday, with 83 people from Alexandria, Louisiana, and continued on Monday with 34 people from Brownsville. "The message is clear: That they shouldn"t migrate. Here in Guatemala, the government is looking after them," said Manuel Rodriguez, head of Guatemala"s migration institute, after the third flight landed in Guatemala City on Wednesday. The new rapid expulsion policy, which has also begun for Salvadoran and Honduran migrants, comes after U.S. Vice President Kamala Harris visited Guatemala in June, telling migrants: "do not come." President Joe Biden"s administration has said it is working on offering more ways for Central American migrants to legally enter the United States.