The oil company BP used a remote-controlled submarine to shoot chemical dispersants into the underwater site where oil is leaking from a wrecked drilling rig.
The action, approved by the E.P.A. is a sign the leak could continue for an extended time. The AP reports that crews are hoping to thin the oil, which is rushing up from the seabed at a pace of about 210,000 gallons per day.
Engineers are trying to concoct other ways to stop the flow of oil. An attempt at capping the leak with a massive concrete dome failed over the weekend. An ice build-up inside the concrete structure blocked the company's attempts to pump the oil out into a tanker.
Near the Louisiana coastline, National Guard helicopters are dropping 1-ton sandbags to plug gaps in barrier islands in a bid to protect sensitive marshlands.