JAKARTA, Indonesia: Indonesia sent bird flu samples to the World Health Organization as part of efforts to lure tourists back to Bali island, a health ministry official said.

Indonesia recently stopped sharing samples with international scientists searching for mutations, saying it wanted assurances that any vaccines developed from its H5N1 virus strain would not be prohibitively expensive.

Samples were sent to the WHO-affiliated Centers for Disease Control and Prevention in Atlanta last Thursday to prove to the world "that the virus has not mutated in any way ... and that Bali is still safe to visit," health ministry spokeswoman Lily Sulistyowati said on Monday.

Experts fear the virus will mutate into a form that spreads easily among humans, potentially sparking a pandemic. Currently, most human cases are linked to contact with infected birds.

Tourists have been slow to return to Bali since al-Qaida-linked militants launched suicide strikes in 2002 and 2005 that together killed more than 220, mostly foreigners.