Cairo - A scorching heatwave gripped Egypt this week, killing at least 42 people, including a German resident, patients in a psychiatric hospital and detainees, officials said on Tuesday.Egyptian summers are usually hot, but this week's temperatures in the south soared to 44°C.The Health Ministry said 21 people died from the heat on Sunday, when temperatures topped 40°C in the country's north. Nineteen more died on Monday, authorities said, mostly elderly citizens.A German national living in the southern city of Luxor died on Tuesday from heatstroke, according to security official Essam el-Desouki. Egypt's official MENA news agency said he was in his sixties.A 62-year old Egyptian in the southern city of Assiut also died Tuesday, health official Ahmed Anwar said.Most of the fatalities - at least 26 - were in Cairo, a crowded, sprawling city of at least 18 million.Three patients at a psychiatric hospital north of Cairo were also among the dead. Three detainees in a jail north of Cairo died because of the heat, said a security official, who spoke on condition of anonymity because he was not authorized to talk to reporters.Egyptian prisons and detention facilities are notoriously overcrowded. The official spoke on condition of anonymity because he was not authorized to speak to reporters.Compounding the woes from the heatwave was a widespread power outage on Tuesday in several Cairo neighbourhoods that lasted a few hours and briefly brought the city's subway to a halt.The Ministry of Electricity blamed the outage on increased consumption that briefly knocked out a power transformer in western Cairo. In rural and southern Egypt, power cuts are usual.