Prosecutor Dimas Guevara told The Associated Press on Wednesday that people have continued to die this year even though the tainted medicine was pulled from shelves in October. Some of the victims struggled for months before dying.
Previously Panamanian authorities had confirmed only 51 deaths from the medicine.
A chemical commonly found in antifreeze and brake fluid, diethylene glycol was used in cough syrup, antihistamine tablets, calamine lotion and rash ointment made in a Panama government laboratory.
Investigations revealed the chemical was made by a Chinese company that fraudulently passed it off as 99.5 percent pure glycerin, a sweetener commonly used in drugs, to a Spanish company. That company sold it to Panama's Medicom SA, which sold it to a government laboratory.
Panamanian officials also exhumed the corpses of victims who died last year and conducted forensic tests that revealed they had been killed by the medicines.
The 293 suspected cases were brought to the police by family members, but the causes of death have not yet been confirmed by forensic tests, Guevara said.
Three Medicom executives are being held in prison, charged with crimes against public health in connection with the deaths.