An investigation was launched in Brazil Monday after an 88-year-old woman was almost buried alive when a hospital declared her prematurely dead, Brazilian newspaper G1 reported.

A death certificate was issued Dec. 22 for Dona Maria das Dores da Conceicao after doctors noticed she had no vital signs. They cited high blood pressure and clogged arteries as the cause of death, and a funeral was planned.

From there, she was due to be taken to a cemetery, but  workers preparing her for burial at a funeral parlor in the eastern city of Ipatinga noticed signs of life.

She was returned to the hospital in Jaipur, still in the coffin, where doctors confirmed she was not dead. But efforts to keep her alive failed, and Friday she died from heart failure.

Officers were investigating a potential medical error in the case