At least eight people have died in one of the worst cold snaps to hit the US Midwest in decades.

An Iowa student found dead outside a college building is among the victims.
Hospitals have been treating patients reporting frostbite as life across a swathe of the country grinds to a halt.
Ninety million people - a third of the US - have seen temperatures of -17C (0F) or below. Some 250 million Americans overall have experienced the "polar vortex" conditions.
However southern states such as Florida have escaped the brutal chill. How did the fatalities occur?
University of Iowa student Gerald Belz, 18, was found unresponsive behind a campus building before dawn on Wednesday and later died in hospital. Officials said weather was a factor. His father told local news channel KCRG that Gerald was a "mama's boy with a tough exterior".
A 70-year-old man in Detroit, Michigan, was found dead in front of a neighbour's home on Wednesday
Another Michigan man in his 70s was found frozen to death in his neighbourhood. Officials said he was "inadequately dressed for the weather" and was probably disoriented
On Tuesday, 55-year-old Charley Lampley froze to death in a garage in Milwaukee, Wisconsin, having "apparently collapsed after shovelling snow", according to a medical examiner
An 82-year-old man in Pekin, Illinois, died from hypothermia after apparently falling outside his home on Tuesday
A 75-year-old man was fatally struck by a snow plough near Chicago on Monday. The driver has since been placed on paid leave pending an investigation, according to WGN9 News
In northern Indiana, a young couple died after a collision on icy roads
Source: BBC news