Two people were badly burned and two others were believed dead after an explosion and fire ripped through a gas station in a small north-central Idaho town, according to officials and company managers.

The blast struck the Atkinson Distributing station in Cardiff, Idaho, just after 3 p.m. on Wednesday, the Clearwater County sheriff’s office said. Two people with severe burns were flown by air ambulance to a hospital in a nearby city. Another two people were taken to area hospitals, though their injuries were not immediately described.

Jeff Adams, a manager with Atkinson Distributing, said the two people flown to a burn center in Seattle were company employees and were in critical condition. He also said there were likely customers in the store when the explosion happened and that some did not escape. Officials said more people were believed to have been inside the building, but they did not release a final count.

By Thursday, investigators and emergency responders were still working through the wreckage. Idaho State Fire Marshal Knute Sandahl said the destruction extended beyond the gas station itself and described a large debris field covering roughly two city blocks. He said structures had been destroyed in addition to the station.

The cause of the explosion was not yet known. Adams said a fuel tanker had been offloading fuel when the blast occurred, but he emphasized that it was too early to say what caused it. Sandahl said deputy fire marshals were at the station and were being assisted by a special agent from the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives.

Cardiff is a remote mountain town with no cell service, which made the flow of information difficult and complicated the initial response, Sandahl said. He said investigators were still sifting through debris and had not yet reached a point where they could give a clearer account of what happened.

The station is normally staffed only during the logging season and includes a small convenience store selling snacks and drinks, according to the company’s website. In a town that small, the destruction of one service point can have an outsized effect, and the extent of the blast suggested the emergency response would continue well beyond the first day.

For now, officials have only a partial picture: a gas station reduced to rubble, multiple injured people taken to hospitals, and at least two others presumed dead as investigators work to establish how the fire started and whether fuel transfer played a role. The sheriff’s office and fire marshal’s office were still gathering details on Thursday.