Falmouth docks have been evacuated after a crane toppled over.
Emergency services were called just before 9.10am on Wednesday and a 200-metre exclusion zone has been put in place.
Devon and Cornwall Police said there were no reports of any injuries but Cliff Road was closed to the public.
A force spokeswoman said officers were assisting with a "full yard evacuation".
Properties are also being evacuated, she added.
Emergency services have declared a major incident.
Navy Lookout tweeted: "Crane at A&P Falmouth just collapsed on RFA Tidespring in drydock. Enormous bang & sirens sounding. Hope no casualties.
"Fortunately RFA Tidespring undamaged - Crane collapsed on the dockside. Assume no injuries but yard evacuated."