(CNN) -- The number of suspected heat-related deaths reported by health officials across the South and Midwest in the past week reached at least nine Wednesday as temperatures continued to hit triple digits.
The health department of Kansas City, Missouri, said Wednesday that the Jackson County Medical Examiner was investigating the city's fourth suspected heat-related death since Friday.
In Tennessee, Shelby County Medical Examiner Karen E. Chancellor said a 77-year-old man was found dead Tuesday evening in his Memphis home. His death resulted from natural causes, but heat was ruled to be a contributing factor.
In Bartlett, Tennessee, a 67-year-old man collapsed in his yard Friday while mowing the lawn, Chancellor said. He died from chronic illnesses but heat exposure was ruled to be a contributing factor.
In Mississippi, a 48-year-old Gulfport man died of heat exposure Monday, according to the county coroner.
The man was working on road construction and "had cramped in the upper extremities," said Jackson County, Mississippi, Coroner Vicki Broadus. "It was his first day on the job as a concrete smoother."
And an 81-year-old Monroe County, Mississippi, woman also died of heat stroke on Saturday, said Monroe County Coroner Alan Gurley.
The Alabama Department of Health said one man died of heat exposure last week. No other information was available.
The National Weather Service said heat advisories and excessive heat warnings are in effect from the southern and central plains through the lower Mississippi and Tennessee river valleys.
The heat index -- what the temperature feels like when combined with the humidity -- is soaring across much of the South. CNN meteorologist Sean Morris said that at 10 a.m. Wednesday the index in Memphis, Tennessee, was at 108 degrees; Little Rock, Arkansas, was at 106; and Jackson, Mississippi, was at 104.
Morris said the heat indices could peak around 120 degrees later Wednesday.
Those at greater risk of heat-related illness include infants and young children, people 65 or older and those who are already ill, especially with heart disease or high blood pressure.
Some helpful tips for cooling off from the Jackson County, Missouri, government website:
-- Avoid liquids containing alcohol or caffeine.
-- Schedule outdoor activities before noon or in the evening.
-- When temperatures reach into the 90s, a cool shower can offer more help than a fan.
-- Wear lightweight, light-colored, loose-fitting clothing, wide-brimmed hats and sunscreen.
-- If you must work in the heat, monitor the condition of co-workers and ask them to do the same for you.