A major fire has broken out on oil and gas barge off New York City's Staten Island. Witnesses say they heard a large explosion shortly after 15 Hours Universal Time at the Exxon facility, followed by a massive fire. Billows of dark smoke blanketed the area, but the blaze appears to be subsiding. Some media are reporting that the blaze may have occurred while a tanker was being refueled. A spokesman for the FBI in Washington says it is too early to pinpoint the cause. He added the Bureau is monitoring the situation because the facility is the type considered vulnerable to terrorist attacks. There have no immediate confirmation of injuries.