JAKARTA, Indonesia (AP) — Indonesian police said a smoke grenade exploded Tuesday near the presidential palace in Jakarta, wounding two soldiers.

Jakarta Police Chief Gatot Eddy Pramono said the two soldiers were exercising in Jakarta’s National Monument Park when they spotted the non-lethal grenade on the ground. He said it exploded when they tried to pick it up.

The soldiers were in stable condition at an army hospital with injuries to their hands and thighs, Pramono said.

He said a bomb squad was sent to secure the park, which is located just across from the presidential palace and other government buildings.

The blast occurred a day after tens of thousands of Muslim conservatives held a gathering near the park. Jakarta police spokesman Yusri Yunus said they were investigating whether the grenade was inadvertently left behind by one of the more than 9,000 police and soldiers were deployed as security at the event