The US government has called on BP to confirm reports of an oil seepage close to the capped well in the Gulf of Mexico.
The energy giant however remains confident the capping device is working and even thinks it could stay in place until two relief wells have been drilled.
But there are concerns that while the oil is being held back the pressure is slowly building and that could spell trouble.
If the pressure under the cap increases oil could start leaking from the sea floor causing irreversible damage. And scientists say the oil which has already polluted the sea is likely to affect marine life for decades.