BBC: Researchers say they have found more than 500 bubbling methane vents on the seafloor off the US east coast.
The unexpected discovery indicates there are large volumes of the gas contained in a type of sludgy ice called methane hydrate.
There are concerns that these new seeps could be making a hitherto unnoticed contribution to global warming.
The scientists say there could be about 30,000 of these hidden methane vents worldwide.
Previous surveys along the Atlantic seaboard have shown...