PF & ESI Liability

Dear All,
We are in turn key projects and awarded various project in Assam, Bihar & orissa. we are sub contracting some erection works to sub-contractor, who don't have any PF & ESI registration, but that sub contractor is sub contracting that work to some other sub contractor who have PF & ESI number and also that sub-contractor is complying all his compliances.
My quaries:
1. Whether we are liable for PF & ESI, if Sub Contractor along with his invoices attached his sub contractor PF & ESI Challan copy along with the his agreement copy.
2. whether is necessary for sub contractor to take registration for PF & ESI in every and every State if he has registration in West BENGAL.All the workers of sub contractor is from west Bengal & he is complying all the formalities in west Bengal.
Kindly advice urgently

1. Sir, so far as compliance under ESI Act, 1948 and rules/regulations framed thereunder is concerned a principal employer is liable for compliance in respect of all employees of his contractor or sub-contractor etc. The main issue is whether compliance is actually made and whether at the time of verification of records of principal employer whether the contractor or sub-contractor produces all the records to the satisfaction of inspecting authorities regarding compliance made. If, the contractor or sub-contractor fails to produce any satisfactory records at the time of verification, the inspecting authorities are within their right to claim contributions on all the amounts detected during such inspection.

2. Any employer whether he is principal employer or in actual a contractor who has obtained ESI Code Number can obtain sub-code as per procedure laid down by ESIC in respect of employees working in other State. If he will not obtain sub-code, it will be difficult for employees posted in other States to get themselves registered under said Act and obtain benefits as and when needed.