Six people have died and five others remained on life support after a rare condition known as "thunderstorm asthma" struck Melbourne, Australia, officials said Sunday.

The sixth victim died in a hospital on Saturday night from medical complications stemming from a wild thunderstorm that struck Australia's second-largest city Monday night, a Health Department statement said.

Storm clouds gathered Monday over Melbourne, Australia, before a major thunderstorm unleashed an outbreak of a rare form of asthma. Australia Bureau of Meteorology

Five patients remained in intensive care units, three of them were in critical condition, the statement said. Twelve more patients were in hospitals with less serious respiratory and related conditions.

Monday's storm caused rain-sodden ryegrass pollen grains to explode and disperse over the city, with tiny pollen particles penetrating deep into lungs. About a third of patients who suffered asthma attacks Monday reported never having had asthma before.

The storm overwhelmed emergency services and hospitals in the city of 4.5 million people, with 8,500 receiving hospital treatment.

The world's first recorded thunderstorm asthma event occurred in Melbourne in 1987, when hospitals reported a five-fold increase in asthma cases. Similar events have happened in the United States, Canada, Britain and Italy. The last major event in Melbourne was in November 2010.