Cops from the West Bengal Criminal Investigation Department (CID) on Tuesday visited Trinamool Congress chief and former CM Mamata Banerjee's residence-cum-party headquarters in Kalighat, Kolkata, as part of its probe into allegations that signatures of several MLAs were forged on a document submitted to the assembly speaker.A CID team paid a visit to Trinamool Congress chief Mamata Banerjee's Kalighat residence-cum-party headquarters. (ANI)Track live updates hereA team of the agency reached 30B Harish Chatterjee Street around noon. They were accompanied by personnel from the Kalighat police station and a large contingent of women police officers, news agency PTI reported.ALSO READ | How Mamata is losing her party, brick by brick, 28 years after she built itWhy the CID went to Mamata’s houseThe CID visited the party headquarters after TMC national general secretary Abhishek Banerjee, who is Mamata's nephew, told investigators that party MLAs had signed the document at the central office.Acting on that information, the agency went to the premises as part of its probe. That said, party leaders did not allow the team to enter, saying any search could take place only in Abhishek Banerjee's presence. The two sides briefly argued before the CID team left, reported PTI."We have not allowed the CID to enter the premises in the absence of Abhishek Banerjee. Once he comes, the CID can carry out its search," senior TMC leader and former MP Subhasish Chakraborty told reporters.Later in the day, the agency returned with more police personnel and entered the former West Bengal CM's residence. Officers from the Kalighat police station intervened after a brief argument with security staff and allowed the search to proceed, as per PTI.The CID then began its verification exercise inside the premises. Another team also visited Abhishek Banerjee's office on Camac Street as part of the investigation.ALSO READ | Who's Yusuf Pathan batting for? Slog-overs specialist turns mystery spinner in games within TMCWhat is the TMC forged-signature row?The row began after rebel TMC MLAs Ritabrata Banerjee and Sandipan Saha accused party leaders of using forged signatures on documents submitted by Abhishek Banerjee to the Assembly.The documents related to the appointment of senior TMC leader Sovandeb Chattopadhyay as Leader of Opposition. The two MLAs claimed that no such resolution was passed at the legislature party meeting on May 6 and alleged that the records were prepared later.The allegations led to an FIR on charges of cheating, forgery and criminal conspiracy. The CID took over the case on May 28 and formed a five-member Special Investigation Team (SIT).Investigators have since questioned several TMC MLAs. According to officials, some legislators told the agency that the signatures shown as theirs were not genuine. The CID has also sought original documents from Abhishek Banerjee.The controversy soon spiralled. Fifty-eight of the TMC's 80 MLAs rebelled against the party leadership, backed Ritabrata Banerjee for the Leader of Opposition's post and won recognition from the Assembly Speaker. The revolt led to the first formal split in the TMC since the party was founded in 1998.Mamata Banerjee meets Sonia GandhiMamata Banerjee met Congress parliamentary party chairperson Sonia Gandhi in New Delhi on Tuesday, PTI reported. The two leaders reportedly exchanged views on opposition unity and the changing political scene in Bengal.Their conversation followed Monday's INDIA bloc meeting, where Banerjee and Gandhi were seen interacting amid renewed efforts by opposition parties to present a united front against the BJP.