A day after Central Bureau of Investigation (CBI) director Ranjit Sinha was asked by it to respond to the "very serious" allegations against him, the Supreme Court issued another notice to him, seeking his explanation over the controversial visitors' logbook at his Delhi residence. A bench led by Chief Justice R M Lodha issued a notice to Sinha on a plea seeking his removal from the probe into the coal block allocation cases. The plea by NGO Common Cause, a petitioner in the Coal scam cases, has also asked for a special investigation team to probe. Another bench led by Justice H L Dattu had on Monday sought his response on disassociating him from 2G cases. Sinha is in a midst of controversy over the visitors' logbook, which showed frequent visits by some of the accused in the 2G and coal block cases among others. Stating that it may scrap decisions taken by Sinha "at a later date," the Supreme Court had on Monday asked the agency chief to reply to the "very serious" averments against him.