The force will not comment on the stick's contents
A police force has undertaken an urgent hunt for a computer memory stick after admitting it has been lost by an officer on duty.
West Midlands Police would not confirm or deny reports that the data stick contained information on terrorism.
The Home Secretary has been informed of the blunder, as has the Independent Police Complaints Commission (IPCC).
It is the latest in a line of high-profile losses of sensitive equipment by public bodies.
A force spokeswoman said searches are being conducted to recover the item and added: "We will not comment in relation to the contents of that memory stick."
The IPCC said it is treating the matter very seriously and has launched its own inquiry.
It will look at the circumstances surrounding the loss, procedures in place at the force which aim to protect sensitive information and whether they are compliant with legal requirements on data protection.
A spokeswoman said the inquiry was likely to last "some months".
The body was asked to investigate when two HM Revenue and Customs CDs containing the personal details of 25 million people were lost last year.
Len Jackson, IPCC Commissioner, said: "This is an extremely serious matter.
"I will ensure that we carry out a timely and proportionate investigation.
"It is important that we establish the facts in this case and identify any lessons to be learned in order to reduce the risk of such incidents occurring again."