CONTRA COSTA COUNTY (KRON) — Crews have contained and cleaned up radioactive material that spilled at a construction site in Antioch, according to Contra County County Fire officials.

Fire dispatch received a call at around 9 a.m. informing them of a possible hazardous material situation, fire officials said.

The situation happened near the Twin Creek Apartments at 1111 James Donlon Blvd.

A piece of construction equipment was damaged and leaked a “very small amount of radioactive material,” Robert Marshall of Contra Costa County Fire said.

Marshall says they believe the environment has been exposed to cesium and americium. These materials are found in certain smoke alarms and are used in medical and industrial settings, Marshall said.

About 50 units in eight nearby apartment buildings were evacuated as a precaution. Residents have been allowed back in their homes

There is no shelter in place in effect, but 50 units in the apartment complex were evacuated. They have since been allowed back into the complex.

A hazardous materials team, fire crews, PG & E and the county’s water district all responded to the incident.

Roads near the construction site on Tabora Drive were closed while crews were cleaning up the hazardous material.

All roads in the area are now open, Marshall said.