Police have lifted a cordon at downtown Athens' Syntagma Square after a chunk of metal initially believed to be an old mortar shell was identified as a machine part.
The bomb scare near the country's Parliament was sounded earlier on Tuesday after workers conducting maintenance on a water line on the corner of Nikis and Ermou streets struck metal.
Greek riot police and troops used water cannon and tear gas on Wednesday against hundreds of migrants as they made another attempt to cross the border from Turkey into Greece.
Plumes of black smoke drifted above the Kastanies border crossing, and a fire engine raced by to put out smoldering blazes. Greek soldiers also fired warning shots into the air.
Migrants amassed at the Greek-Turkish border made about 9,600 attempts to enter Greece overnight, Deputy Defense Minister Alkiviadis Stefanis said Sunday.
All attempts were successfully thwarted, Stefanis said before leaving for the border area.
At the border crossing of Kastanies, there are at least 3,000 migrants waiting to cross into Greece, authorities estimate.