A hazardous materials team was investigating a blast that injured one person inside a business at 9870 Marconi Drive near Michael Faraday Drive in Otay Mesa, near the Mexico border, San Diego Fire-Rescue Department spokesman Lee Swanson said.
A fire sparked inside an electrical panel at the business, according to fire officials.
About hour after the blast, fire officials turned the investigation over to San Diego police after several marijuana plants were found.
Medics have taken the victim to Sharp Chula Vista Medical Center with non-life threatening injuries.
SkyFOX flew over the warehouse and there was no visible damage to the outside of the building.
In October 2004, authorities uncovered a nearly six-ton stash of marijuana in a storehouse at the same site, according to the U.S. Drug Enforcement Administration.