Sound Transit officials said the substance was by-product from tunnel drilling operations

It sounds like something from a B-horror movie.

A mysterious goo exploded out of the ground on Capitol Hill along Pike Street near Boylston Avenue on October 6.

"Somebody reported that they heard a pop and they saw this geyser 20-25 feet in the air," said James Woodbury, Seattle Fire Department Deputy Chief.

The goo bubbled and itched its way across Pike Street.

"I looked out the window and realized there was some stuff coming out of the ground," said Darren Belcher who was nearby at the time.

Belcher said he rushed to get his car out of the way.

Firefighters arrived on the scene. Not knowing what the substance was, they kept everyone at a safe distance.

Sound Transit attempted to determine what happened.

"We took a gas monitor reading. We had no indications that there's any explosive levels," said Bruce Gray with Sound Transit.

Sound Transit said there's no mystery - it was the by-product of their tunnel drilling.

"It's essentially soap and water," said Gray. "It's got some dirt mixed in with it from the mining operations."

An observation well that wasn't properly capped allowed the goo to escape.

Across the street at the Honey Hole sandwich shop the special of the day was the "gooch." It was just a coincidence that the "gooch" was featured while mysterious goo was flowing outside. For those who watched it happen, they said the scene outside was "more funny than scary."