Another elderly patient in Gifu Prefecture has died at a hospital where air conditioning units had broken down amid a heat wave that has gripped the country, police said Wednesday, bring the death toll there to five.

The fifth fatality was an 84-year-old male patient who passed away Tuesday evening at Y&M Fujikake Daiichi Hospital in the city of Gifu. The hospital had denied that the air conditioning failure was the cause of the four earlier deaths, saying that fans were put into use after the air conditioning units malfunctioned.

The police received a report on Monday evening that four people had died at the hospital possibly due to heatstroke after the air conditioners broke down. They have launched an investigation into the deaths on suspicion of professional negligence.

A 52-year-old man who identified himself as the guardian of the patient who died Tuesday consulted with the police two hours after his death at 6:40 p.m., citing the four previous fatalities reported at the hospital. The police said the medical facility did not report the fifth death to them.

The earlier four were two men and two women aged 83 to 85 who were staying on the hospital’s third and fourth floors. They died between 8:40 p.m. Sunday and 11:35 a.m. Monday, according to the police.

Air conditioning units in at least 10 rooms on the hospital’s third and fourth floors were not working at the time. Some patients were moved to second floor rooms with air conditioners, but the first four patients who died were left behind, according to the hospital and the police.

It was not immediately clear where the fifth patient was staying at the time of his death.

The hospital, which specializes in treating the elderly, said the air conditioners broke down on Aug. 20 and that it was using fans in an attempt to keep patients cool because repairs were expected to take about a month.

“The patients’ conditions could have taken a sudden turn for the worse at any time,” Yosei Fujikake, chief of the hospital, told reporters while denying any link between the air conditioners’ failure and their deaths.

Prefectural and city government officials inspected the hospital on Tuesday based on the law concerning hospital management.

The temperature in the city of Gifu rose to as high as 36.2 Celsius on Sunday, according to a local meteorological observatory.

Japan is in the midst of record-setting summer heat that killed 133 people in July, an unprecedented high for a single month. In the week through Sunday, 5,890 people were taken to hospitals for heatstroke or heat exhaustion, according to the Fire and Disaster Management Agency.

While it is common to suffer heat exhaustion and heatstroke outside, people can also get those symptoms while indoors.

Elderly people are said to be particularly vulnerable because they tend to have limited ability to control their body temperatures.

The hospital has a capacity for up to 119 patients in chronic phases of illness and about 50 were staying at the hospital at the time of the deaths, according to the city of Gifu.

Some family members of patients there have visited the hospital to discuss the possibility of having them transferred to different facilities.

A 44-year-old man from Ogaki, Gifu, whose 76-year-old mother has been hospitalized for cerebral infarction, said his mother was moved from the third floor to the second floor, but he wants to transfer her to a different hospital because he saw six beds squeezed into a room suitable for two or three.