Retention of passport by CBI

Sir/madam, i have a uncle who was the secretary of a masjid general body. he resigned and went for job purpose to Malaysia. a worker was murdered from the masjid. my uncle is suspected in the murder case just because he had some telephonic conversation. because of the same reason the called by the local police, special squad and crime branch of Kerala police. the case hasn't proved and the honorable high court handed over the case to CBI. Now the CBI has called him from Malaysia and he was appeared by the respect of the police and the public justice as he did when the former agencies were dealing with the case. Now the CBI is retained his Passport without any signed or official notification. they are not giving back the passport and the validity of the visa is going to expire on this April. Because of the age problem the Malaysian visa will not be renewed once it is expired. so what should he do? Is there any possible way that he can take back hid passport by suing in the court or anything? hoping for a better reply