Someone inflicted damage on the bridge erected over the Rio Moín to provide access to the APM Terminals construction site, said the Consejo Nacional de Vialidad.
The damage resulted in the Consejo closing the access road so that experts can analyze the damage and provide a report, it said.
The container handling terminal is a $1 billion project that is designed to propel Costa Rica into the forefront of sea cargo efficiency.
The project is strongly opposed by the union and members who work on the public docks in Moín and Limón. However, officials seeking a motive for the vandalism may also consider environmentalists who have battled unsuccessfully the construction of the access road because it intrudes on mangroves.
Radical environmentalists have been known to vandalize other construction projects.