That is: a manhole cover on Bush Street blew off near the intersection with Stockton Street just a few blocks from Union Square around 11:30 a.m. this morning.

Bystanders in the area report the block was closed to traffic while two fire trucks and two PG&E vans cleaned up the scene. The only casualty seems to be the rear bumper of a late model red Ford Focus. KRON 4 reports one bystander may have been injured.

A few years ago, SFist wondered what was causing all the manhole covers downtown to explode. The official word from PG&E at the time was that the explosions were due to "burning secondary mains." Which is not at all terrifying.

Update, 2 p.m.: Reader Santiago Santos sends in video of SFFD cleaning the messy aftermath.

"We know a power cable failed," PG&E spokesman Joe Molica told Bay City News unhelpfully, "but we don’t know why.”

A bystander and an employee of the nearby Moth and Dagger Tattoo studio said he could see smoke and fire coming from the exposed manhole after the cover blasted about four feet in the air and banged into the rear of the red Ford.

Previously: All exploding manhole coverage on SFist.