A woman and her 10-year-old daughter died after being poisoned by carbon monoxide fumes as they slept on a moored motor cruiser on Lake Windermere, initial findings of a marine accident investigation have indicated.
Exhaust fumes from a generator, whose improvised exhaust and silencer system had become detached, had spread into the cabin where Kelly Webster, 36, and daughter Lauren Thornton, who were on an Easter boating holiday, were asleep.
"The boat's carbon monoxide sensor system did not alarm because it was not connected to a power supply," said an interim report by the Marine Accident Investigation Branch (MAIB).
The incident was on the Bayliner 285 motor cruiser Arniston on April 1 - Easter Monday - this year. Ms Webster and Lauren, both from Leyland in Lancashire, were on board with the vessel's owner Matthew Eteson, 39, who was Ms Webster's partner and also from Leyland.
The MAIB's report, in the form of a safety bulletin, said: "A bank holiday weekend on board an 11-year-old Bayliner 285 motor cruiser ended tragically when a mother and her 10-year-old daughter died. Initial findings indicate the deceased were poisoned by carbon monoxide."
The bulletin went on: "A 'suitcase' type portable, petrol-driven generator had been installed in the motor cruiser's engine bay to supply the boat with 240v power.
"The generator had been fitted with an improvised exhaust and silencer system which had become detached from both the generator and the outlet on the vessel's side.
"As a result, the generator's exhaust fumes filled the engine bay and spread through gaps in an internal bulkhead into the aft cabin where the mother and daughter were asleep."
The MAIB continued: "When the owner of the boat awoke in the boat's forward cabin, he was suffering from carbon monoxide poisoning but was able to raise the alarm. The mother and daughter could not be revived. The boat's carbon monoxide sensor system did not alarm because it was not connected to a power supply."
The MAIB said the incident raised a number of safety issues and warned boaters to be vigilant and recognise the signs of carbon monoxide poisoning, which was "a silent killer". The bulletin added that the correct positioning and the regular testing of any carbon monoxide sensors was essential. A full MAIB report into the incident will follow later.