31.   The Food and Drug Administration approved AmBisome for use in treating presumed fungal infections in patients with depressed immune systems and fever of unknown origin, or febrile neutropenia.

32.   The safety board said an electrical spark of unknown origin inside the tank likely ignited the fuel vapors.

33.   The sights include iguanas, caves and the Ayo rocks, which are huge boulders of unknown origin.

34.   The universe is either open or filled with an energy of unknown origin.

35.   Then, a second explosion of unknown origin ripped through the mine, trapping the would-be rescuers.

36.   They were even more intrigued when they learned that there are several large Indian mounds in Hancock County, of unknown origin and dating back hundreds of years.

37.   Police are attributing half a dozen deaths in Vancouver and four more in the suburbs to a very pure type of heroin of unknown origin.

38.   A fire of unknown origin caused substantial damage to a home for asylum seekers in the central German city of Neuss.

39.   According to the council, initial evidence traced the cloud to radioactive scrap metal of unknown origin melted down at the plant at the end of May.

40.   An oil slick of unknown origin has reached the shores of southern Finland and threatens a natural conservation area in the region, authorities said Tuesday.