The three sister submarines of HMCS Chicoutimi, which was left drifting in an Atlantic storm when fires affected her propulsion system, are to be kept alongside while the cause of the fires is investigated.

Chicoutimi had been in the hands of the Canadian Navy for just days when the fires crippled her more than 100 miles to the west of Ireland – a fire which killed Lt Chris Saunders and seriously injured two other crew men.

After being pounded by high winds and heavy seas for two days, a tow line was passed to the boat and she was brought back to Clyde Naval Base at Faslane in Scotland.

Now Vice Admiral Bruce MacLean, Chief of Maritime Staff, has announced the move, which he described as a matter of prudence.

“Earlier today, the President of the military Board of Inquiry into the HMCS Chicoutimi incident advised me of preliminary information which caused me to decide that it would be prudent to keep all submarines alongside until more analysis can be done on the possible causes of the fire,” Admiral MacLean declared in a statement issued yesterday.

“With this information I consulted the Navy’s Sub Safe organisation and have subsequently ordered the submarines to remain alongside while we analyze this initial information.”

Chicoutimi’s sisters are HMCS Victoria, currently in Esquimault, British Columbia, and HMC ships Cornerbrook and Windsor, both of which are in Halifax, Nova Scotia.

The Board of Inquiry, headed by Commodore Dan Murphy, has already convened in Scotland and started to gather and analyze evidence on the incident.

The four former Upholder-class boats were bought in a deal in 1998 which cost the Canadians $750 million.

For this the Canadian Navy obtained four modern, quiet long-range diesel-electric patrol submarines to replace their ageing Oberon-class boats.

The four Upholders had been laid up in 1994 as a result of cuts following the end of the Cold War, and were reactivated to Canadian specifications by BAE Systems at Barrow-in-Furness, where Vickers built the boats.

Each submarine has undergone a rigorous trials programme to test the hull, equipment and crew – according to the Canadian National Defence website at www.forces.gc.ca each of the Victoria-class boats on average spent some 30 days at sea before they were accepted by the Canadian Navy.

In the case of Chicoutimi, there were 37 days of sea trials out of Barrow, involving a series of short voyages and periods alongside to validate systems and correct any problems.