Apple has removed it’s online Check Activation Lock Status page. The page allowed people to check the status of an iPhone, iPad, or iPod Touch by plugging in the International Mobile Equipment Identity number or serial number. 

Activation Lock was security feature intended to prevent the use of lost or stolen devices. Apple hasn't said why it removed the site, but some reports said it could be connected to a scheme that allows hackers to steal valid serial numbers from existing iOS users.