No need to panic, yet, but yesterday Washington D.C. firefighters discovered a mysterious, still-unidentified substance inside a just-opened 40-year-old safe. All that's known about the substance so far is that it "exhibited a chemical reaction to water," as the Washington Post put it.

After the mysterious discovery, nine fire trucks, several ambulances, and a full hazmat team rushed to the scene, and authorities shut down the house's street. On-scene tests couldn't identify the substance, though firefighters eventually ruled out the possibility that it was an explosive or some sort of chemical weapon.

At 3 a.m., more than 11 hours after firefighters first arrived, the safe was finally removed from the home and taken to an environmental lab for testing.

"We took the extra precautions," DC fire department spokesman Timothy Wilson told the Washington Post. "We wanted to be as thorough and careful as possible when we moved it."

[Image via Shutterstock]