RIGA, (AFP) - Latvian rescue and medical services tried Thursday to calm panicked members of the public after three cases of a rare atmospheric condition known as ball lightning were reported in the Baltic country over the past week. The unusual phenomenon involves "luminous globules" that can move along solid objects or even float in the air and can cause burning or melting.

Latvian Authorities recommended residents keep windows closed and unplug appliances during electrical storms after local media gave wide coverage to the incidents of the unexplained atmospherical phenomenon. Witnesses had to be treated for shock after two of the incidents, while an apartment caught fire in the city of Smiltene, northeast of Riga, in a third incident on Monday, according to the national fire service.

The apartment appears to have melted. All the furniture, appliances, walls and ceiling seem to have melted from the high temperature, the director of the region's fire service, Andris Vejins, was quoted as saying by the BNS news agency. Never in my career as a fireman have I seen anything like it, he added. The owner of the apartment was not at home at the time and no one was reported to have been injured in the accident.

Also called globe lightning, the phenomenon usually occurs near the ground during thunderstorms, may be red, orange, or yellow in colour, and is often accompanied by a hissing sound and distinct odour. The balls may range in size from one centimeter to one meter (half an inch to one yard) and has been reported to float around people, usually lasting only a few seconds before dying out suddenly.

Its causes are unknown, but explanations for the phenomenon include: air or gas behaving abnormally, high-density plasma, an air vortex containing luminous gases and microwave radiation within a plasma shell.