Sun, sea – and stick-up: Pacific island Aitutaki in shock after its first ever bank heist

The pace of life is languid, to say the least, on Aitutaki, an idyllic coral atoll in the South Pacific. Described as "the world's most beautiful island" by Tony Wheeler, the Lonely Planet co-founder, it is also extremely devout, with more than 20 churches for a population of fewer than 2,000.

Now locals are in shock after news that Aitutaki – one of the Cook Islands – has had its first bank robbery. Police are refusing to say how much was taken from the tiny branch of the Bank of the Cook Islands, except that it was a substantial sum. They have also refused to confirm reports that the bank was secured by only a single padlock.

The island's Mayor, John Baxter, described the robbery as "a very sad occasion" for Aitutaki. He told Radio New Zealand: "I think it is the first time that any of the banks have actually ever been robbed on this small island... [where] everybody knows everybody." Mr Baxter said he suspected that an outsider was responsible for the robbery, which is believed to have been carried out one night last week. According to some reports, $164,000 (£99,000) was taken. Many islanders kept their savings at the bank.

The Cook Islands – a self-governing nation in free association with New Zealand – is a popular tourist destination. Aitutaki is the most visited spot after Raratonga, the main island. Visitors wax lyrical about its pristine beaches, turquoise lagoon and laid-back locals.

Now Aitutaki's image has been dented by the robbery and its three banks have been forced to step up security. Police are trying to ascertain whether the crime was carried out by one or more people and have appealed to the public for information. They say it appears that the premises were thoroughly scouted beforehand.

Detective Inspector Areumu Ingaua told Radio New Zealand: "We believe that the person responsible may have had prior knowledge of the layout of the bank.

"And we also believe, because of the large amount of money stolen, that the offenders may be talking about it with friends and associates, and spending more than usual."

If anyone is splashing the cash on Aitutaki, it will not be long before someone notices. The island has a permanent population of just 1,800, living on seven square miles. Extra police officers have been sent over from Raratonga to help with the investigation.

Aitutaki, which embraced Christianity in 1821 after a visit by an English missionary, is reputed to have the most churches per capita in the world. They encompass more than a dozen faiths.