container TEUs, 60,000 automobiles, and 121,000 metric tons of cement. Other major forms of cargo processed at the port include petroleum, liquefied natural gas (LNG), gypsum, and salt. There were 328,305 cruise ship passengers that year. Some 114 vessel calls are scheduled for the 2016 cruise season. In the wake of the September 11, 2001 attacks, there have been concerns about the security of LNG shipments within Boston Harbor, and increased fear of terrorism. Because of the location of the LNG terminal in the Mystic River, tankers traveling to and from the facility are forced to pass directly offshore of downtown Boston. During their voyage through the harbor, they are protected by a security zone that extends in front of the vessel, behind it, and more than half a mile on either side. This zone is enforced by escort vessels provided by the Coast Guard and State Police. The Tobin Bridge is closed as the escort passes under it, and boating is forbidden within the security zone. , there have been proposals to construct an offshore LNG facility on either Outer Brewster Island in the Harbor, or further afield in the wider Massachusetts Bay. The MBTA operates commuter boats between Long Wharf and Rowes Wharf on the downtown Boston waterfront to Hingham, Hull, Quincy, and Logan Airport as well as inner harbor ferries between downtown Boston, Charlestown, and South Boston. Other fast passenger ferries operate to Provincetown and Salem. Several companies operate cruise ships on the harbor, whilst water taxis operate from various points on the downtown Boston waterfront, Logan Airport, Charlestown, East Boston, and South Boston. Ferries are also provided for travel amongst the harbor islands. There are occasionally marine accidents, as with a commuter ferry Massachusetts going from Boston's Rowes Wharf to Hull in June 2006. Port Police The Massachusetts Port Authority (Massport), which itself was constituted in 1956 maintains its own police force of POST certified and sworn law enforcement officers of the Commonwealth of Massachusetts. They work in conjunction with the Massachusetts State Police—Troop F who also provide law enforcement services for Massport. Massport police officers also known as "Port Officers" are responsible for physical security and law enforcement at the marine terminals, Boston's Seaport District, East Boston parks and various other properties and lands owned by the authority. International seaports agreements – Port of Dalian, China (2005) – Panama Canal Authority, Panama (2005) Memorandum of