According to the Houston Marathon Committee, a 74-year-old man had a heart attack around mile 16. He was taken to the hospital where he later died.
The committee says another man who had just finished the full marathon also suffered a heart attack. Officials say the 50-year-old is expected to survive.
"On behalf of the Houston Marathon Committee, we would like to express our most sincere condolences and support to their family, friends and running communities," said the committee. "Please keep both of these men and their families in your thoughts."