It was also revealed yesterday that residents had been kept in the dark for more than a month about tests conducted last month which found levels of dioxin, a chemical compound linked to cancer, were four times what was allowed under the company's environmental licence.

MM Kembla reported initial test results to the Environmental Protection Authority (EPA) in late March after it found levels of dioxins and furans from the company's horizontal billet caster (HBC) were more than four times the 0.1 nanograms per cubic metre limit.

The EPA yesterday confirmed the machinery, which had been shut down for routine maintenance for a week prior to the EPA receiving the results, would remain inactive until the issue was resolved.

It would be allowed to start only for testing purposes.

MM Kembla confirmed a second round of tests results received this week identified dioxin readings of 17.2 and 12.9 nanograms - 172 and 129 times the allowable limit.

It is unclear whether the EPA has been made aware of the most recent results.

MM Kembla told the Mercury it was "questioning the validity" of the results, saying there were several anomalies with the tests.

"We are awaiting the full suite of results," chief executive Col Weatherstone said yesterday.

He said the company had enough stockpiled product to continue manufacturing its copper tubes without the caster, while the other part of the business, which deals in copper wiring and rods, has not been affected.

Mr Weatherstone said the company was committed to upholding its environmental responsibilities and would work closely with the EPA to resolve the issue, including installing new filters and frames to better capture and filtrate emissions.

Meantime, residents are furious they were not told of the increased dioxin levels immediately.

Port Kembla anti-pollution campaigners Olive Rodwell and Helen Hamilton said people living close to heavy industry had a right to know what was going on in their backyards.

"I'm very concerned about them keeping that type of information from us," Mrs Rodwell said.

"They [MM Kembla] had the opportunity to come to our meeting in April and let us know about this. Otherwise, what are we doing having these meetings?"

EPA chairman Barry Buffier yesterday admitted the issue was made public only after Mrs Hamilton raised the matter with the EPA this week.

"As the HBC was already shut down and there was no immediate [further] health risk the EPA decided to have MM inform the community of the exceedances at a planned Port Kembla Pollution meeting on May 4, when further testing had been conducted and the EPA had a better understanding of the extent of the breach," Mr Buffier said.

The May 4 meeting has now been moved to May 11.