Three retired firefighters who were at ground zero after the Sept. 11, 2001 terrorist attacks have died on the same day from 9/11-related illnesses. The three men, Lt. Howard Bischoff and firefighters Daniel Heglund and Robert Leaver, died Monday, according to the Associated Press.

One had leukemia, one had colon cancer, and one had esophageal cancer, the AP reports. Fire Commissioner Daniel Nigro said their deaths were “a painful reminder that 13 years later we continue to pay a terrible price for the department's heroic efforts."

More than 30,000 9/11 responders and survivors have an illness or injury related to the 2001 terrorist attacks on the World Trade Center, according to the Uniformed Fire Officers Association. Of those, more than 800 New York Fire Department members and 550 NYPD officers have serious illnesses, including cancers, and have retired from their jobs for health reasons. Seventy firefighters and 60 NYPD officers have died from their 9/11-related illnesses, according to the association. It is unclear whether or not that includes the three firefighters who died Monday.

The association said Bischoff, Heglund and Leaver showed signs of health problems not long after 9/11. Heglund retired from the New York Fire Department in March 2003. Bischoff and Leaver retired in May of that year, CBS New York reports.  

Those who were exposed to high levels of dust in the aftermath of the World Trade Center collapse were more likely to develop respiratory symptoms, lung and sinus problems, and asthma, according to the City of New York. Other illnesses related to the attacks included heart disease, gastroesophageal symptoms, and mental health symptoms including post-traumatic stress disorder, or PTSD.