DENVER (CBS4) – Denver police and firefighters investigated a suspicious package dropped off at a fire station Friday night.

The station is at 45th and Tennyson in northwest Denver. Firefighters noticed a suspicious device inside and called out the hazmat team and bomb squad.

Officials said it was a “sure stop” fire grenade. That’s a glass bulb filled with liquid that was used in the early 1900s to put out fires.

It’s not known if someone dropped it off to be safe, or if it was meant to harm someone.