The National Investigation Agency, set up in the aftermath of the Mumbai [Images] terror attack, will probe only the 'gravest' incidents of crime and a team of officers is already in place to handle such cases.

"As I speak, orders have been issued for the appointment of one deputy inspector general, two superintendents of police, two deputy superintendents of police and two inspectors," Home Minister P Chidambaram [Images] said while replying to questions in the Lok Sabha.

He said only the gravest cases of crimes will be taken up for investigation by the NIA, which will operate in a concurrent jurisdictional framework.

"There is a team in place to take up the investigation into any case referred to the NIA," he said adding, "happily, no such incident has occurred since the NIA was set up."

"The NIA will take up cases referred by the states and in rare instances, take up cases in a suo motu manner," Chidambaram said.

Replying to a query, he said the NIA will not take up the investigation into the Mumbai terror attack case as the probe was 'almost complete and the Mumbai police is poised to file a chargesheet' in the matter.

Asked whether the NIA would probe Naxal attacks, Chidambaram said such cases "may not be fit cases for the NIA. A decision would have to be taken on a case-by-case basis."