Crown shares fell 3.6%, which contrasted with a rally in the broader sharemarket to a record high

Australia has ordered an investigation into allegations immigration officials gave casino operator Crown Resorts preferential treatment by fast-tracking visas for Chinese gamblers, the attorney general said on Tuesday.

The probe follows several media reports that claim Crown hired travel agents with ties to drug traffickers to bring Chinese gamblers into Australia, knowingly laundered money at its casinos and had Chinese gamblers' visas expedited.

Attorney General Christian Porter told parliament he had referred the allegations made relating to government officials to the Australian Commission for Law Enforcement Integrity. The ACLEI, an anti-corruption watchdog responsible for investigating federal agencies, would then decide if a further probe was needed.

"It is my view that there are sufficient concerns raised at least to warrant further investigations," Porter said.

Crown said it would assist with any investigation but rejected "allegations of illegality" made in parliament and recent media reports.

"We believe these allegations are ill-informed and an attempt to smear the company," a Crown spokeswoman said.

"If there is any evidence of unlawful conduct, we encourage individuals or organisations to contact the relevant authorities."

Crown shares fell 3.6%, which contrasted with a rally in the broader sharemarket to a record high.

Porter said if ACLEI did not consider the allegations warranted an investigation, the agency would provide the attorney general with an explanation as to why it came to that conclusion, which he would then make public.

The Age and the Sydney Morning Herald newspapers and the "60 Minutes" television programme reported that Crown hired tour operators with ties to drug traffickers to bring wealthy Chinese gamblers into its Australian casinos.

The reports also alleged an Asian crime syndicate laundered money through the Melbourne-based company's casinos, and that the company received preferential treatment from immigration officials which resulted in fast-tracking Chinese gamblers' visas.

Crown on Monday reiterated previous statements on Monday that it has a comprehensive anti-money laundering programme and a robust process for vetting junket operators.

The ACLEI oversees complaints made against the anti-money laundering agency AUSTRAC, the Australian Federal Police, the Department of Home Affairs and the Australian Criminal Intelligence Commission, according to its website.