According to NBC4 News:

A water main described as “colossal” break flooded streets in the Beverly Grove area of Los Angeles Tuesday morning.

The broken 6-inch main shot a geyser of water into the air, causing a sinkhole and flooding streets.

“It was colossal,” a longtime resident of the block told NBC 4. “The jet of water was easily as tall as the tree.”

“That’s a stab in the dark when you say, ‘What caused the water main break?’” said Kirk Broyard of the LADWP (LA Department of Water and Power). “But again, aging infrastructure.”