(CNN) -- An explosive device hidden inside a newspaper exploded when a Vacaville, California, man picked it up near his doorstep Sunday morning, a city official said.
The wounded man was airlifted to a hospital, and residents of a dozen neighboring homes were evacuated, Vacaville city spokesman Mark Mazzaferro said.
It was not immediately known if the victim was targeted or if any other bombs may be hidden at other homes, Mazzaferro said. His condition was not immediately known.
No other explosive devices have been located, but a bomb squad from Travis Air Force Base and federal investigators are combing the neighborhood with explosives-sniffing dogs in the Brown's Valley section of the town, he said.
Residents have gathered at a community center while the search and investigation is conducted, he said.
CNN's Chuck Johnston contributed to this report.