Led by BJP leader Mukul Roy's son Subhrangshu, who was suspended by the Trinamool for six years for "demeaning the party", at least three other MLAs and several councillors reached the capital where they will be drafted into the BJP in the presence of its President Amit Shah.
Besides Subhrangshu, MLAs Gautam Das of Gangarampur and Tusharkanti Bhattacharya of Bishnupur are likely to cross over to the saffron camp.
Another MLA, Sunil Singh, is also believed to have travelled to Delhi to join the BJP.
BJP sources claimed that CPI-M MLA from Hemtabad Debendra Nath Roy would also join its fold. A CPI-M source confirmed that Roy had indeed gone to Delhi in his bid to switch sides.
BJP's newly-elected Barrackpore MP Arjun Singh, who deserted the Trinamool after being denied ticket from the constituency, has seemingly played a key role in engineering the defections.
Sunil Singh is Arjun Singh's relative.
Beside the MLAs, 18 councillors of Halishahar, 17 of Naihati and 14 of Kanchrapara areas are likely to join the Bharatiya Janata party (BJP), party sources said.
Once they switch allegiance, the Trinamool could lose control of all three municipalities.
A beaming Mukul Roy claimed in Delhi that the saffron outfit could take control of up to 60 municipalities in the near future.
"I feel in the next two-three months the BJP will wrest 55-60 municipalities in the state," he said.
Confirming the development, Bhattacharya, who has already reached Delhi, said: "I have heard around four MLAs are joining the BJP today."
During the Lok Sabha campaign, Prime Minister Narendra Modi, Shah and other BJP leaders had claimed that around 100 Trinamool MLAs could join the BJP once the general election got over. Modi had even said that 40 Trinamool legislators were in touch with him.
The BJP came up with a stunning performance capturing 18 of the state's 42 Lok Sabha seats as against only two it won five years back.
The Trinamool, which had bagged a whopping 34 seats in 2014, saw its tally plunging to 22.
The Congress seat count was halved to two from four while the CPI-M failed to open its account. The Marxists had triumphed in two seats in 2014.
( With inputs from IANS )