(NEXSTAR) — A 76-year-old woman who was declared dead at a hospital in Ecuador astonished her relatives by knocking on her coffin during her wake, and the incident has prompted a government investigation into the hospital.

Relatives left the coffin behind and rushed retired nurse Bella Montoya back to the hospital after the wake Friday in the central city of Babahoyo.

Montoya was declared dead on Friday at Hospital Martín Icaza de Babahoyo, according to local outlet El Comercio. She had been initially diagnosed with a cerebrovascular accident and doctors weren’t able to resuscitate her after she went into cardiorespiratory arrest, according to the Ministry of Public Health. The doctor on duty then pronounced her dead.

It wasn’t until hours later when relatives were holding a wake for Montoya that they realized she wasn’t dead.

“There were about 20 of us there,” said her son, Gilberto Barbera, according to the Associated Press. “After about five hours of the wake, the coffin started to make sounds. My mom was wrapped in sheets and hitting the coffin, and when we approached we could see that she was breathing heavily.”

Her son says it gave them all “a fright” when they heard strange noises. Though he and relatives rushed her back to the hospital Friday, she was still in serious condition Monday.

Health officials are currently investigating the incident and the hospital’s procedures when it comes to issuing death certificates.

The Associated Press contributed to this report.