The highway, located about 1,300 miles (2,100 kilometers) north of Santiago, was opened for all kinds of vehicles.
"Carabineros (Chilean police) are giving the necessary instructions on speed and precautions," said Ximena Valcarce, mayor of Arica.
The mines are a remnant of occasional border tensions between Peru and Chile resulting from a mid-19th century war that ended with the transfer to Chile of a portion of southern Peru and Bolivia`s entire Pacific coastline.
The Chilean military planted thousands of anti-personnel and anti-tank mines in a mountainous border area called Los Escritores in 1975, when the country was ruled by General Augusto Pinochet.
Heavy rains on Monday dislodged some of them, causing them to wash onto the heavily traveled Route 5.
"The mines came down toward the northern Route 5, and with the carabineros and the army, a decision was taken to close the highway," Valcarce said.
More than 300 Chileans and 200 Peruvians were stranded in nearby towns by the road closing, according to local media and Chilean foreign ministry reports.
Valcarce did not say how many mines were dislodged during the rains but she said police bomb disposal experts had detonated four explosive devices found on the highway.
Chile has been working to de-mine the area since 2004 under an international treaty banning anti-personnel mines.