US health officials are investigating the death of a three-year-old Venezuelan girl travelling with her parents on a bus carrying asylum seekers from Texas to Chicago.

Thousands of migrants have been sent from Texas to Democratic Party-run US cities under a controversial scheme.

The girl was taken to a hospital in southern Illinois and pronounced dead on Thursday.

Texas officials confirmed her death on Friday, but did not share more details.

The bus set off from the city of Brownsville, on the border with Mexico. Before it left the state, passengers had their temperature assessed and were asked if they had any medical conditions, Texas officials said.

Officials said when it was noticed that the girl's health appeared to be deteriorating, the bus "pulled over and security personnel on board called 911".

Officials from the Texas Division of Emergency Management said that "every loss of life is a tragedy".

Republican governor Greg Abbott of Texas has sent more than 30,000 migrants to cities controlled by the Democrats since last year under his "Operation Lone Star" policies.

Last month, the US department of Justice sued Mr Abbott for his refusal to remove a floating barrier placed on the Rio Grande river aimed at stopping migrants from entering the US from Mexico.

The latest tragedy comes weeks after an eight-year-old girl died at a US border patrol site in Texas.

Venezuela's refugee crisis is the world's second largest. More than seven million Venezuelans have left since 2015 due to the country's political and economic troubles.