The explosion from a small bomb could flood commuter train tunnels between New York and New Jersey in a matter of hours, according to a new government analysis that suggests the PATH rail system is more vulnerable than initially thought, a newspaper reported Friday. The draft analysis, obtained by The New York Times, showed that the PATH system's four tunnels are structurally fragile enough that the damage from a bomb small enough to be carried onto a train could allow 1.2 million gallons (4.56 million liters) of water per minute to gush into a tunnel and flood the system. About 230,000 people use the PATH system each weekday. A spokesman for the Port Authority of New York and New Jersey, which runs the PATH system, defended the system's safety. "If we believed in any way that passengers were in danger, we'd close the system," spokesman Marc La Vorgna said. "That would happen immediately."