A technician on Thursday challenged BP's claim about how long it would have taken to install an additional number of a key device the oil giant had been warned was essential to prevent a significant gas flow problem in its Gulf well that later blew out.

Centralizers make sure the casing is running down the center of the well bore. If the casing is cemented off-center, there is a risk of an imperfect seal that could allow oil and gas to escape.

BP installed only six, against a Halliburton recommendation to install 21.

One issue in a federal investigative panel's probe of the rig explosion and massive oil spill that followed is whether BP cut corners to reduce costs. The well project was nearly $60 million over budget at the time the centralizer warning was raised.

Four days before the April 20 Deepwater Horizon rig explosion in the Gulf of Mexico, a BP well team leader asserted it would take 10 hours to install the additional 15 centralizers. But technician Daniel Oldfather told the joint U.S. Coast Guard-Bureau of Energy Management, Regulation and Enforcement investigative panel it would have taken him only four to eight hours to do the job.

Oldfather, who works for oilfield services firm Weatherford, flew to the rig on April 16 with the 15 centralizers on board, but a pallet of screws and epoxy was missing. He testified that a BP engineer told him when he arrived that the missing materials would be sent out on a boat and arrive later the same day.

Oldfather said the materials never arrived and that he was told the next day the job had been canceled. He said he was never told why and he never raised any objections over any safety concerns because it was BP's decision to make.

The testimony was part of the panel's fifth session of hearings aimed at determining the cause of the explosion and how regulation, safety and oversight can be improved.

The explosion killed 11 workers and led to more than 200 million gallons of oil spewing from BP PLC's undersea well. BP owned the well and was leasing the rig from owner Transocean Ltd.