21.   GHB, also known as the date-rape drug because it can cause blackouts when mixed with alcohol.

22.   Heavy use of air-conditioners in the capital also pushed power consumption to record levels, threatening to cause a blackout.

23.   It was not immediately clear what caused the blackout, but attacks Sunday night damaged two power plants and they have yet to be completely repaired.

24.   It was not immediately clear what caused the blackouts.

25.   Karen Shock, a housing development manager, said residents came to her to ask what had caused the blackout.

26.   National Power Corp. officials said the blackout was apparently caused by a surge and failure in a power distribution line.

27.   One of the shells hit a power transformer in Tulkarem, causing a blackout, witnesses said.

28.   Shortages caused rolling blackouts in northern and central California over two days last month.

29.   Supply power to most of the country failed, causing widespread blackouts.

30.   Technicians eventually said software problems caused the blackout.