The cyanide leak at the site of Tuesday's blast in the Pretoria suburb of Villieria, had been contained by Friday morning and most residents had returned to their homes, police said.
Residents were evacuated for a second time on Thursday after wind stirred up cyanide-contaminated dust.
The cyanide was discovered on Wednesday by experts combing the rubble of the explosion. Investigators believed a container of cyanide, stored in the same garage as the explosives, was damaged in the blast and leaked fumes overnight.
Police spokesperson, Captain George Francis, said police were still combing the blast scene for clues on Friday.
Three people were killed and eight others were injured when a stockpile of commercial explosives, allegedly stored in the home of a professional blaster, detonated on Tuesday morning.
Three houses were flattened and six others rendered uninhabitable.
After the second cyanide scare, about 200 people living in 26th, 27th and 28th avenues were evacuated to the Villieria East Dutch Reformed Church, said clergyman Chris Lotter on Thursday night.
Medical teams screened residents for symptoms of cyanide poisoning.
At least 15 people, who complained of headaches and other irritations, were taken to hospital for observation and treatment, he said.
Derrick Barrett, the professional blaster who owned the house at the centre of the blast, appeared briefly in the Pretoria magistrate's court on Thursday.
He was granted R5 000 bail on Wednesday night.
Barrett, 58, faces three charges of culpable homicide and another of contravening the Explosives Act. - Sapa