The government of El Hierro posted a yellow alert — second level in a scale of four — Sunday and closed some hillside roads and a tunnel to avoid possible injury by falling rocks.
The island's 11,000 residents have been told to monitor communications by the civil protection authority. The island was shaken late Saturday by a 4.3-magnitude quake. Seismic activity began in the area on July 17.
Like all the Canary Islands, El Hierro was formed by volcanic activity. It has some 500 volcanic cones.