SAN DIEGO (CBS 8) - A fire investigation is underway after flames break out near a nursery around midnight at the intersection of Vega Street and West Morena Boulevard.

Firefighters say flames spread to half an acre between the train tracks and Armstrong Nursery. Two fences had to be damaged at the nursery so fire crews could reach the flames.

Firefighters extinguished the blaze within 30 minutes.

"There were some shopping carts found against the fence unknown what their purpose was," said Battalion Chief Matt Nilsen with San Diego Fire-Rescue. "There is a lot of homeless in the area unsure at this point if it was related, and we've got investigators coming to determine a cause."

Investigators say recently there have been several fires started in the area.