The radioactivity scare along the southern coast Tuesday was a false alarm, according to the Consejo Nacional de Vialidad, the road agency.
The agency ordered the highway shut for miles from the site where a truck mishap damaged a densitometer at a sewer installation.
The device that measures the compacted soil contains a radioactive element.
The site was on the Costanera seven kilometers north of Palmar Norte.
The agency said it turned out that the radioactive section of the device is protected by a sturdy capsule so there was no release from the source. The road was re-opened by 7:30 p.m. Tuesday, the agency said.