CAIRO — A poet and activist hit with a blast of birdshot from a police shotgun during a march to lay flowers in Tahrir Square in Cairo died because she was too thin, a spokesman for Egypt’s medical examiner said late Saturday.

The poet and activist, Shaimaa el-Sabbagh, was killed on Jan. 24, a day before the anniversary of Egypt’s Arab Spring revolt in 2011. Before the marchers could reach Tahrir Square, riot police officers blasted them with tear gas and birdshot at close range as photographers and cameramen watched. Their haunting images of Ms. Sabbagh dying in the arms of another marcher have made her a symbol of the epidemic of police abuse.

On Saturday, though, the spokesman for the Medical Forensics Authority said in a television interview that Ms. Sabbagh, 31, would not have died had she not been so slender.

“Shaimaa el-Sabbagh, according to science, should not have died,” the spokesman, Hisham Abdel Hamid, said, calling it “a very rare case.”