The incident happened at Pattern Energy's recently completed Ocotillo wind project in California, the second incident of its kind in the past six weeks. (see update below).
"These turbines will remain curtailed until it can be determined they are not at risk of a similar malfunction," Siemens said in a statement today.
The manufacturer said it has convened a team of experts at the site who will examine all facets of this incident, including the production, installation, commissioning and service of the blade.
"Siemens does not yet know the root cause of this incident and is working to determine if and how this is related to a recent similar incident in Iowa," the company added.
A blade on the same model of turbine broke off at MidAmerican Energy's 200MW Eclipse wind farm in Iowa on 5 April. No one was injured in either incident.
Pattern Energy brought the Ocotillo project online in December. The company has shut down all 94 turbines that make up the 265MW project, said spokesman Matt Dallas.
"They will not return to operation until they have been evaluated and are deemed safe," he said.
Update (22 May) - A Siemens spokesperson said the company is still investigating the issue.