File Photo – Highland Park Police. | Photo: Max Weingardt.

Police say that the explosive materials found twice last week on a shoreline in Highland Park were a hand grenade and aircraft flares, possibly from World War II.

The Highland Park Police Department responded on April 6 around 2:57 p.m. to the Openlands Lakeshore Preserve, 3136 Patten Road, for a report of explosive materials found.

The City of Highland Park said in a statement that the Waukegan Bomb Squad responded to assist Highland Park police with the situation.

The explosives were found on the shoreline of the lakeshore preserve at the bottom of the bluff, according to the Openlands Lakeshore Preserve.

The explosive, believed to be an old hand grenade, was removed in a “safe and secure manner,” police and city officials said.

Openlands Lakeshore Beach. | Photo: Ignas Vlog (Google Maps).

Police responded back to the same area again on April 9 around 2 p.m. after additional explosives material was located.

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Those materials are believed to be World War II aircraft flares and were located in the same general area.

The entire Openlands Lakeshore Preserve is closed to the public until further notice as an investigation is conducted.

Openlands said they are working with the military and all persons must keep off the bluff and lakefront until the investigation is complete.

“While criminal activity is not suspected, further information is not available at this time. Persons who encounter unknown materials, wherever they may be, should not touch them, immediately leave the area and call 911,” Highland Park police said in a statement Monday.