Fifty-seven people died due to heat-related medical issues in Japan over the week starting July 29, the government said Tuesday, with the number of those taken to hospitals more than tripling to 18,347 from the previous week’s 5,664.

The weekly figure for hospitalizations due to high temperatures was the second highest since tallies began in 2008, according to the Fire and Disaster Management Agency.

Of the 18,347 people, 729 had severe symptoms that will require more than three weeks of treatment as an inpatient, while 6,548 had less serious issues, requiring shorter stays. Those age 65 and older accounted for 54.3 percent of the total.

Tokyo had the most people taken to hospitals at 1,857, followed by 1,342 in Aichi Prefecture and 1,307 in Saitama Prefecture. Deaths were reported across 24 prefectures, with Hokkaido seeing the most at seven, followed by five each in Ibaraki and Saitama.

A high pressure system over the Japanese archipelago preserved extreme heat, said the agency. It is advising people to constantly stay hydrated and rest in cooler areas.