Motorists could be hit by a potential fuel shortage after striking dock workers vowed to stop tankers leaving the Grangemouth terminal.
Industrial action began at the port on Tuesday and is due to continue until March 29 when an overtime ban will begin.
Dockers are unhappy at the introduction of a new shift pattern which they say amounts to a “de facto pay cut”.
The Unite members have been picketing outside the entrance to the docks from Tuesday morning.
However, today they said Forth Ports decision to open up another road into the docks had caused them to picket the entrance to the Ineos terminal.
As lorries and tankers began to queue up, Unite regional officer Tony Trench said the move was the result of the “attitude of the employer”.
He said: “They don’t want to sit down and discuss anything.”
The union official added: “We have now released vehicles to go in but nothing is coming out. This could lead to a shortage of fuel.”
Forth Ports had closed its quayside container operation, while keeping its remaining operations open.
A spokesperson for the Port of Grangemouth said: “Unite’s decision to call a two week strike cannot be justified. We have been discussing with the union proposed changes to shift patterns at the Port of Grangemouth since May 2015. During that time their implementation has been delayed twice to allow Unite to put forward a workable alternative, which they have failed to do.
“Vessels now call at the port seven days a week and increasingly at weekends. Like any modern business, we need the flexibility to respond to our customers’ needs. Our staff and their union accepted the potential need for flexible shift patterns when this element of their employment contracts was agreed in 2011.
“We call on Unite to end this strike, get our people back to work, honour the contracts agreed in 2011 and reopen discussions on these necessary proposals.
“Meanwhile, with the exception of container quayside operations, the remainder of the Port of Grangemouth remains open for business and continues to operate.”
A spokesperson for Police Scotland said: “Police are currently dealing traffic congestion around Gate One of Grangemouth Port on Powdrake Road in connection with the ongoing industrial action. Drivers in the area are advised to leave extra time for their journeys and to find alternative routes where possible.”