An improvised explosive device (IED) described as grenade-type was discovered underwater at a drinking water reservoir in Alabama this week during routine maintenance and inspection work, the Mobile Area Water and Sewer System (MAWSS) said Tuesday.

MAWSS said that after the device was found at the Converse Reservoir dam, it contacted the Mobile County Sheriff’s Office, which coordinated a multi-agency response to recover and safely detonate it.

The Gulf Coast Regional Maritime Response and Render-Safe Team later recovered and safely detonated the device. 

Other agencies involved in the operation included the FBI Bomb Squad, the Alabama Law Enforcement Agency Bomb Squad, the Mobile County Sheriff’s Office, the Mobile Police Department Explosive Ordnance Detail, and the Daphne Search and Rescue Team. 

Officials have not released additional details about the device or how long it may have been submerged before it was discovered. It remains unclear whether it was intentionally placed at the reservoir or discarded unintentionally. No suspects have been identified.

According to MAWSS, the Converse Reservoir, also known as Big Creek Lake, provides drinking water for more than 350,000 people across Mobile and Baldwin counties. It supplies homes, schools, hospitals, and businesses with “award-winning water,” regarded as some of the “cleanest and best-tasting in the country.”

“Our top priority is keeping your drinking water safe,” said Bud McCrory, MAWSS director. “This is an unprecedented threat, and we are fortunate that this device was discovered before it could cause serious damage to our water supply or harm to individuals. We are grateful for the professionalism and competency of our law enforcement partners – as well as the quick thinking of our contractors and divers – in identifying this device and safely destroying it.”

The reservoir and dam are federally designated critical infrastructure. MAWSS said it will continue working with law enforcement agencies to enhance security at the site.