Cement flaws 'known before Gulf spill'

The firms drilling a BP Gulf of Mexico oil well had tests showing cement used to seal it before it blew out was unstable, US investigators have found.

The findings conflict with statements by US oil contractor Halliburton, which supplied the cement and has said tests showed it was stable.

But a presidential panel on the disaster found that three tests prior to the blowout showed the opposite.

The 20 April rig explosion killed 11 workers and caused a massive oil leak. Adam Brookes reports.