The British Petroleum (BP) has attached a cap to a blown-out well on the seabed in its latest attempt to control the massive oil spill in the Gulf of Mexico, the U.S. Coast Guard said Thursday night.

Remotely operated undersea vehicles work to cut and cap the riser pipe at the site of the Deepwater Horizon oil leak as it continues to spew oil into the Gulf of Mexico in this video image taken from a BP live video feed June 3, 2010. [Xinhua]

However, Coast Guard officials told CNN that they are unsure if the new method will succeed in containing the oil spill.

The cap was placed atop the damaged riser pipe of the well, but oil and gas continued to spew, according to U.S. media reports.

BP CEO Tony Hayward said the next 12 to 24 hours will "give us an indication of how successful this attempt will be."

The latest development followed days of setbacks for BP's efforts to cap the well, which is gushing out hundreds of thousands of barrels of oil a day for six weeks.