Video footage has emerged of a kilometre-long crack thought to have been triggered by an underground stream in northwest Mexico.

The eight-metre (26ft) deep trench opened up last week and severed Highway 26 between Hermosillo and the coast.

Captured by Hermosillo Desde El Cielo , the footage was shot by a drone flying along the length of the trench, which is up to five metres (16ft) across.

Farm workers and vehicles have been forced to go around the area due to the unstable ground. Another crack was reported to have opened near Highway 4 in the same area.

Geological investigations are under way into the cause of the crack, according to El Imparcial newspaper.

The civil protection unit said the fissure could have been triggered by an earthquake last Sunday.

The newspaper added that an investigation found that farmers in the area had built up a levee to contain rainwater which had begun to leak, causing an underground stream which undermined the earth above it until it collapsed.