A newborn baby boy is fighting for his life today after oxygen ignited inside a special hospital hood, burning his head and face.

The baby was lying in an open-topped cot under a warmer at Mercy Hospital in Coon Rapids, Minnesota, on Tuesday when the accident happened, Allina Hospital and Clinics said in a statement.

The baby, just 12 hours old and named Maverick, was wearing an oxygen hood, a device that fits over the face to supply additional oxygen, when something caused the gas to ignite, the statement said.

Nurses who were with the baby immediately put out the fire, Allina said. Authorities are investigating how the fire started.

The baby, born three weeks early, was taken to the neo-natal intensive care unit at Hennepin County Medical Centre and is being treated by doctors from the hospital's burns unit.

Hospital chiefs said he was in a medically-induced coma and on a ventilator, in a critical but stable condition.