PENRITH Council has assured the public there is no risk after fragments of glass, stone and crockery were found in the topsoil of some sport ovals.
The main soccer field at Cook Park at St Marys and Cooks and Banks Reserve AFL field at St Clair were among four parks temporarily closed by the council.
Sita, the recycling company working with Penrith Council, was contracted to put the first application of recycled green waste on the Cook Park stadium before the long weekend. It is believed the problem of the fragments had been caused at Sita's Kemps Creek plant.
It has not happened before in the Penrith local government area, a council spokesman said.
"Sita has been unable to identify a cause at this stage," he said.
"Sita is reviewing its systems and processes to determine what happened and why the quality control systems failed.
"The council will be using an alternate supplier until product quality can be assured."
The council stopped the program and fenced off affected areas before the public was put at risk.
"There are no signs at Cook Park because the problem is within the stadium facility, which is surrounded by a 1.8 metre chainwire fence so there is no public access," the spokesman said.
"The other sites have been surrounded with orange parrawebbing, with 'Field Closed' signs placed at the ground."
Sita will reconstruct the affected fields at their cost.
"Ovals are being 'topped'. Turf, soil and glass are stripped by machine from the oval surface," the council spokesman said. "The material is then being removed from site. Turf regenerates over a six-week period.
"The process has started and it's working effectively."
A Sita spokeswoman said a detailed remediation plan had been developed.
"Sita takes this matter very seriously and an investigation is under way to establish the cause," she said.
"Safety remains our primary concern and the work will be undertaken as quickly as practicable."
■ Readers have expressed concern when alerted to the park closures.
"To think they're [Sita] going to look after the radioactive waste going to Kemps Creek. Scary.
"If this can happen to sports fields, what will happen to radioactive waste?" Tony Robinson asked.