The laboratory produces radioisotopes for cancer treatment
Belgian authorities have warned people in the south of the country not to eat locally grown produce after a leak from a nuclear research institute.
A safety alert was issued after a leak of radioactive iodine gas from a laboratory in Fleurus, near the southern city of Charleroi.
Locals have been told not to eat locally grown fruit, vegetables or dairy products as a precaution.
The Belgian nuclear control agency has described the leak as serious.
The authorities have been criticised for initially playing down the incident, which took place earlier this week.
The Institut des Radioelements laboratory halted production on Tuesday, but the leak was initially announced as not representing a risk to residents in the area or to the environment.
However, precautionary measures were eventually taken after grass samples showed higher-than-expected contamination.
Fleurus's population and residents of villages located within a 5km radius have been asked not to eat fruit and vegetables from gardens or drink milk from neighbouring farms, until further notice.
The institute produces radioisotopes for medical imaging and for treating cancer.