At about 9 a.m. crews responded to a report that a piece of equipment used by surveyors was run over by a construction vehicle and spilled out a very small amount of radioactive material of some kind, Contra Costa County Fire Protection District Fire Marshal Robert Marshall said.
"It's not a big leak, it's not severe," Marshall said. "We're trying to determine exactly what the material is."
Marshall said that it doesn't appear that anyone was injured or was exposed to the material.
As a precaution, about 50 units in roughly eight nearby apartment buildings were evacuated, Marshall said. In addition to the fire crews, the county's hazardous materials team responded, as have teams from PG&E and the county's water district.
The construction site is on Tabora Drive, near the intersection of James Donlon and Contra Loma boulevards, which were closed to traffic in the area.
Streets are closed & apartments are evacuated in Antioch bc of an exposed radioactive material. pic.twitter.com/Q4dSGO4NO7— Amy Hollyfield (@amyhollyfield) October 6, 2016