An early-morning fire caused an estimated $90,000 in damage to a West Duluth warehouse on Saturday. There were no reports of injuries.

The first firefighters on the scene of the fire at 414 S. 63rd Ave. West, which was reported at 1:19 a.m., encountered "a fully-involved warehouse fire with explosions going off in the interior of the building," the Duluth Fire Department reported in a news release.

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Crews "immediately declared a defensive mode of operation" and attacked the fire with hoses from outside the building. Initial reports that someone was in the building at the time of the fire were unfounded, authorities said.

The fire caused an estimated $90,000 in damage to the building and its contents, the fire department reported. The cause of the fire had not yet been determined Saturday morning and remains under investigation.