SafeWork SA is investigating whether the operator of the Port Pirie smelter Nyrstar breached workplace safety laws after two of its workers suffered serious burns.

Nyrstar has declined to comment over the incidents which both happened at the smelter on January 3.

In the first, a 53-year-old male worker suffered burns on his face and neck while he was cleaning a hot flue.

Shortly afterwards, a 43-year-old man sustained burns on his feet, thighs and hands while cleaning waste products in the same area.

Both men had to be taken to the Royal Adelaide Hospital for treatment.

SafeWork SA says it will not reveal further details while it investigates if there have been any breaches of work health and safety laws.