Heiman HS2WD-E siren state

Hi,
I’m using a deconz RaspBee II with the deCONZ add-on.
When my Heiman HS2WD-E siren starts up, its status always stays off, its status never lights up.
I can’t use a trigger for an automation based on siren state.
How can I detect when the siren is on?
Thank you for your help.