Horry County firefighters were called to Hague Marina on Hague Drive in the Socastee area for a boat explosion.
It happened just before 1:30 p.m. Thursday.
Just before 2 p.m., a firefighter on his radio said they were "concerned about a second device" and were moving all response crews back from the scene.
Horry County police Sgt. Robert Kegler says they don't believe another explosion will occur, but they evacuated the marina as a precaution.
The State Law Enforcement Division's Bomb Squad arrived on scene in two helicopters. They went into the boat, along with Horry County police's bomb squad, and looked for any evidence of an explosive device.
They didn't find anything and turned the scene back over to Horry County police.
Sgt. Kegler says because of the weather situation tonight, they cannot continue their investigation inside the boat. Officers will remain on scene throughout the night to protect the boat and the area.
The investigation will resume Friday morning.
Horry County Fire Rescue responded to a boat fire on Hague Drive in December of 2012.