OPA-LOCKA, Fla. -

Miami-Dade Fire Rescue on Thursday sent its hazmat team to investigate depleted uranium exposed at Opa-locka Executive Airport Thursday afternoon.

Firefighters forced people to evacuate a 150-foot area around the uranium, Fire Rescue spokesman Arnold Piedrahita Jr. tweeted.

It's unclear what caused the uranium to be exposed. A contractor told Piedrahita that it was located inside a 55-gallon drum near a dismantled plane.

At around 1 p.m., the hazmat team confirmed uranium was inside drum and was monitoring levels of radiation and requested help from the Environmental Protection Agency.

According to the EPA website, depleted uranium is used in helicopters and airplanes as counter weights on certain wing parts.