Australian Border Force (ABF) officers and hazmat teams raided the unit in Arncliffe about 9am and left the scene with tape declaring it a “contaminated hot zone”.
Fire and Rescue NSW (FRNSW) has confirmed it found the radioactive material, which is commonly used in several industries, at the location.
“The material was found in suitable and effective containers, with no release of radiation,” FRNSW said in a statement.
“FRNSW established a 10-metre exclusion zone around the property as firefighters, in protective clothing, used special detectors to inspect the site.
“They were able to further seal the material without incident.”
FRNSW said three people who lived at the address were taken to hospital for observation.
“There was no evidence of exposure… other residents nearby, evacuated as a precaution, have since safely returned to their homes.”
Environment Protection Authority (EPA), Australian Nuclear Science and Technology Organisation (ANSTO) and AFB testing confirmed they recorded regular readings and declared the area safe.
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The raid saw Kelsey Street blocked off at either end, with residents unable to access the street for most of the day.
Earlier a resident told 9News she was worried about the raid.
“It is a very quiet neighbourhood and it sort of stuff is ridiculous anywhere but you don’t expect it to happen right down the street from you,” the resident told 9News.
NSW Police, as well as officers in hazmat suits, and Fire and Rescue NSW were on scene investigating the home.
”People in the vicinity of the location are urged to follow all directions from emergency services,” AFB said in a statement.
“All appropriate safety measures are being implemented.”
Investigations are ongoing.