A Fijian resort at the centre of a suspected alcohol poisoning debacle is said to be cooperating with investigations.

A number of Australians staying at the high-end Warwick Resort are understood to be critically ill after drinking Pina Coladas at its bar.

Fiji Tourism CEO Brent Hill says investigations are underway.

"The resort's been great - they're very distressed, but they have been really helpful. The bar person responsible for serving at the time has been there for 16 years, he's a long-standing employee." 

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• Four Australians critical after suspected cocktail poisoning in Fiji