The hunt for one to three suspects was taking place near a San Bernardino, California, center where as many as 20 people were shot Wednesday, authorities said.
SWAT teams and the bomb squad were working to clear the buildings where the shootings took place.
Witnesses told police they saw three men with long rifles, a law enforcement source told CNN. The source said the suspects got into a black SUV and drove away.
The bomb squad found a suspicious package on the second floor of a building and determined it is "not normal," the source said. They are going to handle it with a robot, the source added.
• There are multiple buildings in the complex, CNN affiliate KTLA reported. SWAT teams are moving methodically through to clear them.
• The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives were responding, agency representatives said.
• Loma Linda University Medical Center is expecting an unknown number of patients from the shooting, spokeswoman Briana Pastorino said. She said the extent of the anticipated patients' injuries is not clear.
• A woman who works at a building where the shootings occurred texted her father: "Shooting at my work. People shot." The father told CNN affiliate KABC his daughter told him 10 to 20 people were shot.