An explosive device discovered on Gress Beach in February may have been left behind after a military exercise at the end of 2013.
The Ministry of Defence (MoD) are unable to say for sure, however.
A Freedom of Information (FoI) request by the Stornoway Gazette found that the Phosphorous Marine Marker, which was disposed of through a controlled explosion by a team from Faslane, was identified as being from France originally, but may have come from either military, search and rescue or private sector operations.
A response from the Navy Command FOI Section said: “It is not uncommon for these devices to wash up on beaches or be trawled by fishermen and, because they have a light metal casing, they can travel considerable distances in the tides and currents around our and other coasts.
“These markers contain just under 0.5kg of phosphorous when new and almost always burn out completely before sinking.
“However when there is any doubt that there may be hazardous traces of phosphorous remaining, a controlled demolition will be undertaken, as was the case on February 9th.”
They added that this particular device was made in France but that the type was available for general use.
“It is not known whether it was used by French forces during the exercise or by another nation,” the Navy Command stated.
“In fact, flares of this nature can be used in military exercises but, as they are also used by fishing vessels etc, it has not been possible to determine whether it was associated with the exercise in Broad Bay last year or had come from elsewhere.”
The Joint Warrior military exercise, which takes place twice a year, began on the west coast this week and is similar to the operation undertaken at the end of last year.
Loch a Tuath councillor Donald Crichton wrote to the MoD earlier this year after the discovery of the device in February to seek assurance over safety for coastal communities when military exercises are taking place.
In the remainder of the FoI statement, the MoD stated: “The MoD is aware of the impact of military activity and has directed that environmental considerations will always be recognised throughout exercise planning and execution.
“Furthermore, close working relationships with landowners and key national stakeholders, combined with engagement with local communities, ensure that appropriate environmental mitigation procedues are put in place and adhered to.”
They pointed out that this was illustrated through the consultation process for Exercise Joint Warrior that ensures Marine Scotland, the Department of Energy and Conservation and Fishermen’s Associations are informed of all planned activity and that a Notice to Mariners is also issued.
They concluded: “I hope you will appreciate that the MoD cannot be held responsible for all the items washed up on beaches around the United Kingdom.
“In most instances, objects found by members of the public are reported to the police or the coastguard who make an assessment and contact the appropriate qualified authorities or personnel.
“Nevertheless, the MoD will, of course, respond when called to assist the civil authorities.”