Geologists are investigating what caused a giant sinkhole to open up in Guatemala City, swallowing an entire intersection.

The hole is 20 meters across and plunges nearly 30 meters deep.

A clothing factory and a house were reportedly lost in the hole, but so far, no deaths have been reported.

Geologists say the cause is still a mystery,

"I can tell you what it's not: It's not a geological fault, and it's not the product of an earthquake," said David Monterroso, a geophysics engineer at the National Disaster Management Agency. "That's all we know. We're going to have to descend."

Crews are waiting for blueprints of the city's drainage system before completing their investigations.

Neighbours said a weekend security guard at the factory was spared because he had left to look after his house, which flooded from heavy rain as Tropical Storm Agatha bore down on Central America. The storm has killed at least 179 people.

Dozens are still missing, thousands have lost homes and emergency crews are struggling to reach isolated communities cut off by washed-out roads and collapsed bridges caused by Tropical Storm Agatha.

Local residents near the sinkhole said it was a miracle no factory workers died.

"The boys were lucky," resident Honora Oliva said. "They left at six that afternoon, an hour before the earth opened up."

Many people living nearby have moved out over fears the hole may expand.

In 2007, a similar sinkhole opened up not far from this week's cavern. Three people died and several homes were swallowed. It was blamed on rain and an underground sewage flow.