PORT-AU-PRINCE, Haiti/CIUDAD ACUNA, Mexico, Sept 21 (Reuters) - Angry scenes broke out at Haiti"s main airport on Tuesday among migrants sent home from a squalid Texan border camp, as U.S. President Joe Biden faced mounting pressure to stop an expulsions policy the U.N. refugee chief said might be illegal. Nearly 10,000 migrants, mainly Haitian, remain in worsening conditions in the impromptu camp that sprang up under a bridge spanning the Rio Grande from Texan town Del Rio to Mexico"s Ciudad Acuna. In recent days, U.S. authorities have removed at least 4,000 people from the site for processing in detention centers. Hundreds have now been returned to Haiti. Returnees reacted angrily as they stepped off flights at Port-au-Prince airport after spending thousands of dollars on arduous voyages from the troubled Caribbean nation via South America hoping for a better life in the United States. On Tuesday, they found themselves back where they started. A group of men in white tee-shirts rushed back towards the plane they had disembarked from, with at least one man trying to reboard, a Reuters witness said. Chairs were thrown and tempers ran high, exacerbated by news the Haitian government had accepted the deportations. "I am angry at the government, we were told in prison that the Haitian government had signed to send us back to Haiti. They are all bad people, these authorities," said Yranese Melidor, 45, who arrived on an earlier flight. The disturbances underscored the instability in the poor Caribbean nation, where a presidential assassination, rising gang violence and a major earthquake have spread chaos in recent weeks. Filippo Grandi, the head of the U.N refugee agency, said U.S. expulsions to such a volatile situation might violate international law and could constitute refoulement, or exposing people seeking shelter to life-threatening situations. U.S. Senate Majority Leader Chuck Schumer also called out Biden on Tuesday, saying it "defies common sense" to expel the migrants to Haiti, and expressing anger over tactics used by border guards to control the crowds at the camp. U.S. Vice President Kamala Harris said the situation was complex and that the United States needed "to do a lot more" to support the basic needs of people in Haiti. "People want to stay home, they don"t want to leave home, but they leave when they cannot satisfy their basic needs," she told reporters. The camp"s population peaked at up to 14,000 at the weekend, according to the U.N"s refugee agency. Fearful of the expulsions, some of the population has now set up a new camp on the Mexican side of the river. Republican politicians with an eye on 2022 midterm elections have been quick to portray the sprawling camp as the result of Democrats" push to end some migration restrictions. Migrants seeking refuge in the U.S. wade through the Rio Grande river from Ciudad Acuna, Mexico toward Del Rio, Texas, U.S. while carrying supplies, in Ciudad Acuna, Mexico September 21, 2021. REUTERS/Daniel Becerril Haitian migrants board an airport bus aftter U.S. authorities flew them out of a Texas border city after crossing the Rio Grande river from Mexico, at Toussaint Louverture International Airport in Port-au-Prince, Haiti September 21, 2021. REUTERS/Ralph Tedy Erol Haitian migrants collect their belongings after U.S. authorities flew them out of a Texas border city after crossing the Rio Grande river from Mexico, at Toussaint Louverture International Airport in Port-au-Prince, Haiti September 21, 2021. REUTERS/Ralph Tedy Erol 1/8 Haitian migrants board an airport bus aftter U.S. authorities flew them out of a Texas border city after crossing the Rio Grande river from Mexico, at Toussaint Louverture International Airport in Port-au-Prince, Haiti September 21, 2021. REUTERS/Ralph Tedy Erol The conflicting demands underscored policy challenges the Biden administration faces as it tries to manage record numbers of border arrivals this year that Republican Senator Mitt Romney on Tuesday called a "disaster." In Texas, three Haitians briefly escaped from a bus traveling towards Brownsville on Monday, according to Jaime Garza, chief deputy at the Kleberg County Sheriff"s Office. The bus was one of two transporting Haitian migrants from the border, he said. The three escaped and ran, but were immediately apprehended, he said. Mexican authorities also prepared flights and buses to its southern states after it began detaining Haitians in Ciudad Acuna, just across the border from Del Rio. The removal transport appeared aimed at reducing the concentration around the camps. A Reuters crew witnessed one encounter, where several migrants yelled and protested as Mexican agents boarded them into a National Immigration Institute (INM) van. INM did not immediately respond to a requests for comment. "HELPING GREATLY" The new camp on the Mexican side has been growing, with migrants there aided by groups, including the Red Cross and Doctors Without Borders, as well as the U.N"s migration agency. Residents from Ciudad Acuna brought food. Surreane Petit, who clutched her 3-year-old boy at her side, said staying in Mexico was a huge improvement over the U.S. camp. "Here the Mexican people are helping greatly." "Over there we were hungry," Petit said. "Under the bridge there was no help, no help." She said she had lived the last five years in Chile, where her son was born, but decided to leave after pandemic lockdowns made it hard to leave her house to find work. Following an outpouring of anger over an incident in which mounted U.S. border agents in cowboy hats used horse reins like whips to intimidate the migrants, U.S. Department of Homeland Security Secretary Alejandro Mayorkas emphasized that U.S. border agents were delivering medical attention and were working with the Red Cross. Mayorkas said he was horrified by the images of the mistreatment, echoing increasingly strident criticism from the White House which said the footage "does not represent who we are as a country." Despite the risk of being returned to Haiti, many migrants remained in the Del Rio camp. Carly Pierre, 40, said he was staying in the U.S. camp because he saw a chance to make it into the United States with his wife and two children, ages 3 and 5, after several years living in Brazil. "There are deportees, and there are people who will make it in," he said, shorts still wet from having crossed the river to buy ice and soda at a convenience store on the Mexican side.