Highway officials now say that there were three major slides and 11 smaller ones that blocked Ruta 32 north of San José Thursday evening.
The Cruz Roja said it evacuated 1,200 motorists and their passengers who were trapped on the highway.
Crews have been working since daybreak to open up the highway, but the work probably will not be finished today especially if the expected afternoon rains materialize, said the Consejo Nacional de Vialidad.
Crews have been working form the north and from the south in the vicinity of the Zurquí tunnel, and the consejo said early in the afternoon that all the vehicles had been freed.
The Instituto Meterológico Nacional said that the atmosphere is unstable and that evaporation from a week of rain is adding moisture to the air. More heavy rains are expected to last into the night. That makes the work sites on Ruta 32 dangerous because rains could provoke more slides.
The weather institute predicted as much as 60 millimeters of rain, more than two inches.
The Ministerio de Obras Públicas y Transporte
and the Policía de Tránsito have been on the job since early evening Thursday. The Cruz Roja said it brought in workers from Heredia, San José and Guápiles to set up two command centers.
The slides contains mature trees, rocks and other debris.
So far no serious injuries have been reported. Ruta 32 is the main road to the northern zone and eventually to Limón.
Thursday saw another series of heavy storms in the Central Valley. The Caribbean coast and parched Guanacaste saw little.
More than an inch of rain fell in San José, according to the automatic stations maintained by the Instituto Meteorológico Nacional. Escazú got 37.8 millimeters or about 1.49 inches. La Fortuna in the northern zone saw 55.4 millimeters by 10 p.m. That is 2.18 inches.
There was flooding, heavy runoffs and flooded storm sewers all over the metro area. Officials are keeping an eye on Ruta 27, the Caldera highway, too where slides are possible.
The weather institute said that the same conditions were likely for today: Hot mornings resulting in heavy afternoon downpours. The prediction said that there would be rain in some sections of the Pacific coast, too.