The Central Bureau of Investigation (CBI) on Wednesday detained Mumbai lawyer Anand Daga in connection with the ongoing probe against former Maharashtra Home Minister Anil Deshmukh..The arrest was made on allegation that Daga paid illegal gratification for getting hold of a document from a junior CBI official in connection with the probe..CBI also reportedly registered an FIR against the lawyer for allegedly trying to influence the preliminary enquiry ordered by the Bombay High Court into the corruption allegations against Deshmukh. .According to sources, CBI officials suspected that a lower rank officer was given illegal gratification in exchange for the internal document of CBI.The document which CBI claimed was leaked on Saturday was a report of the preliminary enquiry supposedly giving a clean chit to Deshmukh and recommending closure of investigation against him. .On Wednesday, CBI questioned Deshmukh's son in law Gaurav Chaturvedi and Daga before registering an FIR against them. They let Chaturvedi go as they did not yet find his involvement in the case. .Sources say that CBI has also arrested the junior officer, sub-inspector Abhishek Tiwari who was in touch with Daga for the document.