A resident reported hearing "a loud bang" outside his home near the corner of Taraval Street and 37th Avenue at about 8:50 p.m., police spokeswoman Sgt. Lyn Tomioka said.
Officers arrived minutes later to find the rack on its side and broken into three pieces, Tomioka said.
"The container appeared to have exploded and burst at its seams," she said.
A bomb squad investigated and concluded that some kind of homemade liquid explosive concoction may have been used, as there was no evidence of charring or burning, Tomioka said.
No suspects were seen and no arrests have been made.
Tomioka said police are not aware of any other similar incidents recently. An arson investigation is ongoing.