Two men have been taken to hospital after a tug collided with a number of safety boats close to the scene of an earlier fatal accident.
Milford Haven could become the UK's third busiest port with LNG
They were thrown into the sea near a liquefied natural gas (LNG) jetty at Milford Haven in Pembrokeshire.
Milford Haven Port Authority said it launched an investigation following the collision at about 0730 BST.
One worker was killed and seven others rescued following the previous incident near the terminal on Saturday.
The port authority said Tuesday's collision involved the tug Smit Barracuda which collided with a number of safety boats.
"Two people were thrown into the water as a result of the incident, but both were rescued and taken to hospital," it said.
"The port authority has ordered all marine activity in the vicinity of the jetty to cease while the investigation is carried out. The rest of the Haven remains open as normal."
In Saturday's accident, a 44-year-old Dutchman whose body was recovered from the water after a platform being used as a support crane collapsed has been named as Adrianus Van Ham.
Specialist engineers are being flown to Pembrokeshire to help secure the platform which has now floated upright.
About eight people were working on the rig and a number of them were thrown into the water.
A major search and rescue operation involving coastguards, police, fire crews and paramedics was launched.
Two men were pulled from the water and five were clinging to the rig.
Mr Van Ham's body was recovered on Sunday evening.