Emergency services gained entry to the flat in Watkin Lane at 5.52pm yesterday (Monday, April 8) and found a woman unresponsive.
She was pronounced dead at the scene.
Police said they are treating her death as "unexplained" at this stage, but have ruled out foul play.
It is the second sudden, unexplained death at the same block of flats in just four days.
On Friday, April 5, police responded to the "sudden death" of a 35-year-old man at the same address.
The cause of his death is also not believed to be suspicious, but the cause has not been established.
Lancashire Police ruled out any link between the two deaths.
Lancashire Police said: "We were called by the ambulance service at about 6pm yesterday (Monday, April 8) to reports of a sudden death at an address on Watkin Lane in Lostock Hall.
"Officers attended and sadly a 41-year-old woman was pronounced dead at the scene.
"Her death is currently being treated as unexplained but at this stage is not believed to be suspicious and enquiries are on-going.
"There is not believed to be any link with the death of a 35-year-old male at the address on Friday, April 5."
A spokesperson for North West Ambulance Service added: "We attended a private address at 5.52pm on Monday, April 8.
"No one was taken to hospital and the incident was handed over to police."