"A precise estimate isn't possible yet," said a Hannover Re spokeswoman. Hannover Re considers a large claim as one that costs the company at least EUR5 million.
The rig, named the Deepwater Horizon, was built in 2001 and would cost more than $600 million to replace, analysts estimate.
The rig was owned and operated by Transocean Ltd. of Zug, Switzerland, and contracted to U.K. oil major BP PLC.
A spokeswoman for Munich Re AG, one of the largest reinsurers worldwide, said it was too early to give an estimate of the claims it expects, but said it is one of the reinsurers of the platform.