The CBI on Friday conducted raids on the premises of 15 Jharkhand MLAs, including labour minister Chandraprakash Choudhary, as part of its investigation into the allegations of horse trading which led to countermanding of the March 30 Rajya Sabha poll.

"Raids were also conducted at the residences of Independent candidate Pawan Kumar Dhoot in Kolkata and former Rajya Sabha member Ajay Maroo in Ranchi," a CBI official said.

Dhoot, an industrialist, was one of the independent candidates in the countermanded Rajya Sabha elections.

The CBI could not search the house of JMM MLA Sita Soren, daughter-in-law of JMM president Shibu Soren, in Bokaro, as it was found locked.

"We have put a seal on her residence and deployed guards there. However, we have conducted raids in another of her houses," the official said.

Thirty-six places were selected for the early morning raid by 36 teams of the premier investigation agency in Ranchi, Jamshedpur, Bokaro, Hazaribagh, Godda, Bihar's Banka district and Giridih.

The other MLAs in whose residences raids were conducted are Sanjay Prasad Yadav, Janardhan Paswan, Sanjay Kumar Singh Yadav (all 3 of RJD), Sudha Choudhary (JDU), Ram Chandra Sahis, Umakant Razzak, Kamal Kishore Bhagat (all 3 of AJSU Party), Paulis Surin (JMM), Arun Mandal, Ramchandra Baitha (both BJP), Saurav Narayan Singh, Anant Pratap Deo, Sarafaraz Ahmed (all three Cong), the official said.

Raids were also carried out in the premises of Yakub Ali, a private citizen, he said.

On April 21, the CBI had raided the premises of three MLAs, Vishnu Bhaiyya (JMM), K N Tripathy (Congress) and Suresh Paswan of the RJD and independent candidate and industrialist R K Agarwal and his kin.

The sleuths had also seized the ballot box, which was allegedly used in the March 30 countermanded elections to the Rajya Sabha, on April 21.

The agency has registered a case under section 171F (undue influence) and 188 of the Indian Penal Code (disobedience to an order lawfully promulgated by a public servant), days after the police and the Income Tax department seized Rs 2.15 crore from a vehicle allegedly belonging to a relative of an independent candidate on the outskirts of Ranchi on the day of the poll.

The EC had conducted fresh biennial elections on May 3 for the two RS seats.