First, it was "toxic seaweed." Then it was a "coincidence."

And now, eight months after a string of tourists began dying after sleeping in nearby Thai hotels, authorities have concluded the cause.

Most of the victims "probably" died from pesticide, announced Thailand's Department for Disease Control.

Authorities maintain that "some toxic chemical, pesticide or gas" likely caused the death of a female New Zealander and a Thai tour guide sleeping next door. The deaths of a British couple who stayed at the hotel is "possibly related." The other three deaths -- there have been six in total -- "might have the same causative agent" or were dismissed as unrelated. All died in the early months of 2011.

The findings are somewhat inconclusive for a months-long investigation that relied on help from the U.S. Centers for Disease Control and Prevention as well as the World Health Organization.

Since the beginning, authorities have been slow to fully investigate the bizarre deaths in Chiang Mai, a northern Thai hub popular with backpackers. Police at first shrugged off the deaths as caused by bad seaweed bought in a nearby food stall. As they mounted, the city's mayor attributed the tragedies to "nothing more than a coincidence."

The most recent findings stop short of assigning blame and do not refer by name to the hotel in which four of the victims died, the three-star Downtown Inn. Relatives of the dead are left wondering exactly who or what happened. Was it the work an overeager exterminator? An off-brand rat poison?

Authorities' feet dragging coaxed some detective work out of New Zealand's "60 Minutes" news program, which stayed at the hotel incognito and scraped carpets and air-conditoners to find the cause. Their consulted experts concluded the culprit was "chlorpyrifos," a bug-killing agent heavily regulated in the U.S. Thai officials insist this agent, however, is not to blame.

Whatever the exact cause, Thailand's health ministry has said it's "confident that such events are sporadic and can largely be averted in the future."

To reassure tourists, officials have vowed to set up a panel to investigate and control pesticides used in hotels and better regulate food stalls. But there is little evidence at this point to suggest any punitive action against whoever sprayed whatever chemical that killed a series of tourists and one Thai tour guide.