DYE testing has been carried out today (Tuesday) to check drainage system connections in the wake of a "major pollution incident" in the River Esk at Musselburgh.

The work is being carried out by officers from the Scottish Environment Protection Agency (SEPA) and involves using luminous green tracer dye which is designed for this purpose and is not harmful to the environment or local ecology.

SEPA and East Lothian Council are continuing to work together to respond to the spillage, which is believed to be oil, petrol or diesel, and was first reported on Friday, January 14.

Survey activity carried out by SEPA ecologists to understand the impact of the pollution incident on the River Esk and its affected tributary was also repeated today. It continues to show that, while the receiving burn is currently heavily impacted, the short-term impact on the river is low.

The council previously stated that a manhole leading to a watercourse had been identified as the source of the pollution.

Water samples have been taken from several locations and are being analysed by SEPA scientists to identify a range of contaminants found which will help to identify the source.

A spokesperson said: "We have continued to closely monitor the river environment in recent days, including over the weekend.

"The various measures installed in the watercourse to contain contamination are working effectively and are being replenished as necessary.

"Clean-up operations continue to progress.

"A tanker was back out on site on Monday and removed a further significant amount of contaminated material from the Craigie Burn.

"While the situation with discoloured water and odour in the River Esk has improved, local people may still observe some discolouration on the surface of the river, as well as the Craigie Burn, which discharged into the Esk, particularly if we experience significant rainfall patterns.

"Frequent multi-agency assessment of progress continues to be made in order to inform further remedial actions, including further deployment of the tanker as necessary."

SEPA and the council have been supported by Scottish Water and the Scottish SPCA.

SEPA is continuing to carry out a range of investigations and assessments to trace the source of the pollution and officers are pursuing a number of lines of enquiry.

Scottish SPCA senior inspector John Toule said: "We are continuing to support the pollution incident at River Esk in Musselburgh.

"We have so far uplifted five swans and taken them to our National Wildlife Rescue Centre to receive the care they need.

"As we need to protect the birds we already have on site from bird flu, we are limited in how many we can take at a time.

"We will keep monitoring the situation and providing care to the birds as space allows.

"We would advise members of the public not to approach the birds.

"If you suspect an animal to be injured or in distress, please call our helpline on 03000 999 999."