In a transatlantic deportation without precedent, Mexico has put 311 Indians - caught illegally entering the country and trying to cross over to the US - on a Boeing 747-400 charter scheduled to touch down at Delhi airport early on Friday.Mexico's National Migration Institute (INM) said in a release that the deportees, who are being escorted back home by 60 federal migration agents, had been found to have entered the country without valid documents for "regular stay" over the past few months.The mass deportation revived memories of the tragedy that befell a family from Punjab in June, when a six-year-old girl died of a heat stroke in the Arizona desert on the US-Mexico border after her mother went in search of water during their illegal border crossing . The body of Gurpreet Kaur was found after two Indian women apprehended by US border patrol revealed that a mother and her two children had been with them until a few hours earlier.Sources said each member of the group possibly paid Rs 25-30 lakh to the agents who arranged their travel to Mexico and promised to help them illegally cross over to the United States.The cost apparently included airfare, accommodation in Mexico and meals. The agents had purportedly cited a week to a month's time to arrange their entry into the US, the sources said. According to the Mexico's National Migration Institute release, they were caught in Mexico without "papers for regular stay" and produced before immigration authorities in the states of Oaxaca, Baja California, Veracruz, Chiapas, Sonora, Mexico City, Durango and Tabasco.US President Donald Trump 's threat to impose tariffs on all Mexican imports if the country did not put a check on people illegally entering US through the porous borders forced its hand, sources said. A source said the Boeing 747-400 that took off from Mexico's Toluca City International Airport with 311 deportees was expected to land in Delhi at 5.45am on Friday."This operation was carried out thanks to the excellent communication and coordination with the embassy of that Asian country (Indian) with which the recognition and return of these citizens was worked under strict adherence to the migration law and its regulations," the INM statement said.The deportees were issued an "emergency certificate" each, which is a one-way travel document that allows an Indian citizen to enter India in an emergency. Such papers are issued to individuals who lose, damage or have no valid passports. INM said never before had Mexico carried out a deportation exercise of this scale.