(CNN) Two Americans, a Dutch national and Swiss national were killed by a hit-and-run driver while cycling in Tajikistan Sunday, officials say.

The four tourists died after a car struck them in Khatlon Oblast, a region south of Tajikistan's capital, Dushanbe. Tajik authorities said three other cyclists in their group were treated for minor injuries. Their nationalities have not been released.

Authorities in Tajikistan investigating the incident are considering "all possibilities," including terrorism and the possibility it was an accident, Umarjonni Emmomali, head of the press department at the Ministry of Tajikistan, told CNN.

Investigators searched the village of Torbulok following the incident and identified a damaged vehicle that showed "involvement in the commission of this crime," according to a statement sent to CNN Sunday from the Tajikistan Interior Ministry.

One suspect was arrested, according to the statement, and "during the resistance" two other suspects were "eliminated." CNN asked the Tajikistan Interior Ministry for clarification on the word "eliminated" but received no response.

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