A major oil terminal in Alaska was temporarily shut because of a possible terrorist threat, it has emerged.
Valdez is a loading point for oil from the trans-Alaska pipeline
The transfer of oil onto tankers at Valdez port, in Prince William Sound, was halted from Tuesday to Thursday.
A US Homeland Security spokesman said it was part of "a continuing effort to ensure the security of our homeland".
The terminal was already subject to restrictions imposed last September, including a prohibition zone of 200 metres around all tankers.
It comes as two flights to the United States were cancelled and others given fighter escorts amid new fears of attacks.
A British Airways flight, BA223, from London to Washington was cancelled on Thursday.
The same flight a day earlier was given a fighter escort into Washington and, once on the tarmac, its passengers questioned and baggage searched.
An Aero Mexico flight from Mexico City to Las Angeles was cancelled on Wednesday, and other Aero Mexico and Air France flights were escorted in by fighter aircraft.
The BBC's Jon Leyne in Washington says it is clear the US authorities have specific information that is causing them great concern, but are giving few details away.
The US has been at Code Orange - the second highest level on a five-step terror attack warning scale - since 21 December.
Russ Knocke, of the Homeland Security department, said the decision to close the port in Alaska was consistent with Code Orange.
It is not known what specifically triggered the decision, but local coastguards said the port had now reopened.
"Right now we are allowing tanker traffic throughout the port," said a spokesperson for the Coastguard's Valdez Marine Safety Office.
"Appropriate safety measures are being taken with regard to the security information that we have".
Valdez is the loading point for oil from the trans-Alaska pipeline, which carries about 17% of America's domestic supply from the Prudhoe Bay oilfields.
Pipeline operator, Alyeska Pipeline Service Co, said production was not interrupted by the two-day shutdown.