Blocks of molten lava as large as three-storey buildings have rolled down a hillside on the Spanish island of La Palma while a series of tremors shook the ground three weeks after the volcanic eruption.

There were 21 seismic movements on Sunday (local time), with the largest measuring 3.8, the Spanish National Geological Institute said, shaking the ground in the villages of Mazo, Fuencaliente and El Paso.

The blocks of red-hot magma flowing down the side of the Cumbre Vieja volcano were the size of three-storey buildings, the Spanish Institute of Geology and Mining said on Sunday.

There was a partial cone collapse near the volcano’s emission vent on Saturday, said Stavros Meletlidis, a spokesman for ING.

“The collapse of the northern flank of the Cumbre Vieja volcano has caused the release of large blocks of material and the appearance of new flows that run through areas already evacuated,” tweeted Spain’s National Security Department.

Rivers of lava have destroyed 1186 buildings since the eruption on September 19, the Canary Islands Volcanic Institute said.

Lava has engulfed 493 hectares of land, said Miguel Ángel Morcuende, technical director of the Canary Islands Volcanic Emergency Plan (Pevolca) organisation.

About 6000 people have been evacuated from their homes on La Palma, which has about 83,000 inhabitants.

-Reuters