Three retired firefighters who worked at Ground Zero have died on the same day from 9/11-related illnesses.

New York Fire Commissioner Daniel Nigro said the deaths are "a painful reminder that 13 years later we continue to pay a terrible price for the department's heroic efforts."

Lieutenant Howard Bischoff, Robert Leaver and Daniel Heglund died on Monday.

One had leukaemia, one had oesophageal cancer and a third had colon cancer.

They were among the hundreds of firefighters who rushed to Ground Zero in the aftermath of the attacks - attending to survivors as they battled the flames and smoke of Ground Zero.

The Fire Department of New York lost 343 firefighters on 9/11. In total, almost 3,000 people died in the attacks.

First responders showed health problems soon after the attacks, with 99% of exposed firefighters reporting at least one new respiratory illness.