The police are attempting to block an alleged attempt to sell millions of personal details allegedly stolen from the National Registration Department.

Bukit Aman Commercial Crime Investigation Department director Kamarudin Md Din said this was the first step taken by the police upon learning of the matter yesterday.

He said the police are also attempting to identify the persons involved in the alleged leak and do not discount the possibility of an inside job.

"We are working to block (the selling). That was the early action...