MEXICO CITY (Reuters) - A 10-year-old Guatemalan migrant girl died after being taken to hospital from a Mexico City immigration detention center, Mexican authorities said on Thursday, adding to a growing number of deaths of minors migrating from the Central American country.

The death comes during the biggest surge of migrants on the U.S.-Mexico border in a decade. More Guatemalans are crossing the border than citizens of any other nation.

Three Guatemalan minors have died in U.S. custody since December, and a Guatemalan toddler died in Texas this week after being released from U.S. Customs and Border Protection custody.

The 10-year-old girl, whose name was not made public, was treated for a sore throat as soon as she arrived at the Iztapalapa Migration Station with her mother on Tuesday after traveling by bus from the northern state of Chihuahua, the National Migration Institute said.

She remained under medical supervision at the center until she was transferred to a children’s hospital. She died late on Wednesday night, the institute said.

Immigration officials did not immediately respond to requests for further information about the family and why they were traveling from the border state back south. It was not immediately clear if she was formally in Mexican custody when she died.