A Norwegian maritime company that surveys and approves safety programs for vessels recertified papers for the Deepwater Horizon on April 21, a day after the rig blew up in the Gulf of Mexico.

The blast killed 11 people and led to 200 million gallons of oil spewing from BP PLC's deep-sea well.

Transocean's safety manager Jerry Canducci testified Thursday at a federal panel investigating the cause of the explosion. Canducci says Det Norske Veritas spent two days in the company's offices and recertified the papers on April 21, while the rig was still burning in the Gulf.

It is unclear why the Norwegian company recertified the rig's paperwork after the explosion.

Transocean had leased the rig to BP, which was the majority owner of the well when it blew up.