ANAHEIM (CBSLA.com) — A pipe bomb exploded Sunday afternoon in an alleyway in Anaheim, authorities said.

The device, according to police, had been placed on the ground near a utility pole at E. Wilhelmina Street and Anaheim Boulevard.

The blast was so strong that it sent the end-cap punching through a wooden structure, creating a round hole in a door.

Investigators say the bomb was made of metal though it remains unclear what type.

The explosion happened near homes with some neighbors reporting that they felt their residences shaking during the blast.

“It was like around 1:30 and I was assisting some customers that were with me. We were talking about a vehicle when we hear the explosion happen in the alleyway,” said Anna Trujillo, who works at a car dealership nearby.

She initially thought there had been a shooting.

“It was too loud to be a shot so we were like, ‘It has to be a bomb.’ And then we see all the white smoke coming out,” Trujillo said. “I was scared.”

It remains unclear what type of explosive material was inside the pipe bomb.

No injuries were reported.