Pakistani investigators have informed the government that they may have to stop their probe into the Mumbai attacks due to lack of cooperation by authorities in India and several other countries.

The Federal Investigation Agency, which is probing the Mumbai terror attacks [Images], has informed the interior ministry in a letter that it would have custody of some suspects only for a few more days and it was thus imperative to get cooperation from the other countries, Dawn News channel quoted its sources as saying.

The FIA said it 'may have to stop further investigations' against the suspects due to the lack of cooperation by India and other countries, the sources said. There was no immediate word from the interior ministry on the issue.

The investigators told the interior ministry that they had not received the Indian police's chargesheet against Ajmal Amir Kasab [Images], the lone terrorist captured for the Mumbai attacks, and other suspects. There was also no response from the Federal Bureau of Investigation and the intelligence agencies of Spain, United Arab Emirates, Kuwait and Saudi Arabia, for requests from Pakistan for information related to the terrorists involved in the attacks.

The FIA had approached these foreign agencies for 'vital information' through Pakistan's Foreign Office, the sources said. The FBI had been requested to help obtain information from Google and Yahoo on two email accounts used by the suspects.

Any further delay in obtaining information from the other countries can affect the probe as the Pakistani suspects would be sent to jail from FIA's custody once their remand period ended.

The sources said no suspect can be kept with police or intelligence agencies for more than 30 days. Pakistani authorities have arrested six suspects in connection with the Mumbai attacks.

Four of these suspects -- Lashker-e-Taiba activists Zakiur Rehman Lakhvi, Zarar Shah, Abu al Qama and Hamad Amin Sadiq -- have been remanded to the FIA's custody till March 17 by an anti-terrorism court. The suspects are facing charges under anti-terror and cyber crime laws. Pakistan officials have said they need further information from India for their successful prosecution.