A top Chinese official on Saturday warned of risky conditions for labourers after a probe found "many" problems following the country's deadliest blaze in over a decade which killed 120 people in a poultry plant.

Huang Yi, chief engineer of the State Administration of Work Safety (SAWS), said the inspection uncovered numerous issues problems including coal mines still operating despite being ordered shut.

"The concept of prioritising has not been firmly established, production still comes first," he said in a report, posted on the department's website.

"And the breaking of laws and violating of rules is still the main reason behind accidents."

The report was based on an interview of Huang with China National Radio.

Fatal accidents are regularly reported at Chinese mines and factories, with many blaming lax enforcement of rules.

Huang said the recent probe, which covered three provinces, found coal mines still operating despite having been told to close.

At one worksite that had had a "major accident" three years earlier, no one had yet been held responsible.

The report did not provide further details about the investigation or its results.

Inspectors would soon visit 13 other provinces and publicise their findings, Huang said.

Authorities have talked tough on workplace safety violations since the deadly blaze at the Baoyuanfeng poultry plant in northeastern Jilin province early this month.

The Supreme Court this week urged the judiciary to "deal severely with crimes that jeopardise manufacturing safety," the Xinhua state news agency said.

Baoyuanfeng factory workers were blocked from escaping the fire because only one of the building doors was open, the Southern Metropolis Daily reported earlier.

Other doors were locked to prevent workers taking toilet breaks, the state-run broadcaster CCTV said.