Costa Rica's Turrialba volcano erupted Tuesday, spewing ash and rocks and forcing 21 people in its vicinity to evacuate their homes, the Volcano and Seismology Observatory said.

"In the afternoon we had a small eruption of the volcano with pyroclastic material, chiefly ash blown by the wind," observatory director Juan Segura told AFP.

The last time the 3,328-meter (10,918-foot) volcano erupted was in 2007, he added.

Authorities issued an alert for the area surrounding the volcano, located 40 kilometers (25 miles) east of San Jose, and said 21 people were evacuated.

Segura said that a team of vulcanologists would climb to the top of the volcano early Wednesday "to make an on-site assessment" of the volcano.

The last major eruption of the Turrialba volcano was in 1856. It has had at least five major explosive eruptions in the last 3,500 years.