An emergency warning siren sounded a false alarm Friday morning in northern Lawrence. The siren, near 1658 East 1550 Road, sounded for one to three minutes shortly before 8 a.m.

It isn’t yet clear why that one, alone among the county’s 39 warning sirens, went off Friday, said Jillian Rodrigue, assistant director of Douglas County Emergency Management. Technicians from Blue Valley Public Safety, the Grain Valley, Mo., company that maintenances the sirens, checked the equipment Friday without finding a clear cause.

Rodrigue said the siren is controlled by a separate piece of equipment from others in the system, and department staff would be watching it in the coming days to see if it functions properly.