Dozens of families have contacted ITV London over the treatment of their loved ones at Basildon Hospital.
The hospital is one of 14 across the country currently under investigation, because of higher than expected death rates.
The probe by the NHS Commissioning Board was ordered in the wake of failings at Stafford Hospital, where neglect and abuse led to hundreds of unnecessary deaths.
For this special report, Paul Brand spoke to two families, who claim the deaths of their relatives following treatment at Basildon Hospital could have been prevented.
More top news
CCTV and images show man suspected of trying to set the north London mosque alight in alleged Islamophobic hate crime
Detectives investigating a man's body washed up on the shores of the river have arrested a second man on suspicion of murder.
Keepers have the celebrating the arrival of the western lowland gorilla to 22-year-old mother Effie in captivity at the zoo.