A powdery substance that was discovered at the White House Sunday evening, prompting a temporary evacuation of the complex, has been sent for further evaluation and testing, the Secret Service said.

A field test determined that the substance was possibly cocaine, according to two sources familiar with the initial report, though such tests are not conclusive. The sources said it was discovered in the West Wing, and one described it as a white powdery substance in a Ziploc bag.

CNN has reached out to the White House and FBI for comment.

Secret Service spokesperson Anthony Guglielmi said the powdery substance was found in a "work area within the West Wing." The Washington, DC, fire department, which deployed its hazmat team, determined that the substance was non-hazardous and an investigation into how it entered the White House is ongoing, Guglielmi said.

The discovery of the substance on Sunday evening triggered a brief evacuation as part of what the Secret Service described as "precautionary closures."

President Joe Biden was at Camp David over the weekend and returned to the White House Tuesday morning.