BROWNSTOWN TOWNSHIP, Mich. -

With just days away until the three-year anniversary of the mysterious disappearance of Lizzie Mae Collier-Sweet, police said they're following up on a new lead.

Collier-Sweet, 49, went missing after her Brownstown Township home caught fire Jan. 8, 2007.

The fire was ruled an arson but investigators said they aren't sure if Collier-Sweet was in the home at the time of the fire.

Police said there's been no communication from her since, and she has not been located.

In an interview Wednesday with Local 4, Collier-Sweet's sister said she's still mourning the loss of her sister.

"It's hard to lose a sibling, or any family. There's no closure, said Louise Collier, Collier-Sweet's sister. "I would feel better if I knew where she was."

But police said they got a letter late Tuesday from an inmate at a Muskegon, Mich., correctional facility claiming that he had information in the case.

Investigators in Muskegon told investigators in metro Detroit that the inmate who sent the letter has been making phone calls about Collier-Sweet's disappearance.

"It's rather intriguing to me as an investigator. It's from Muskegon, all the way on the western part of the state. So I don?t know what connection he would have with this area," said Brownstown Township Lt. Detective Robert Grant. "It's definitely not Roger Sweet. He's in a completely different correction institution."

Roger Sweet, Collier-Sweet's husband, is being held in Ionia, Mich., convicted on criminal sexual conduct charges and of killing his first wife, Marlene Sweet.

Marlene Sweet died in 1990 after a fall in the couple's Farmington Hills home. Her death was originally ruled accidental, but was reopened and eventually ruled a homicide.

Roger Sweet maintains that he has nothing to do with Collier-Sweet's disappearance.

"It was my new year's resolution, to have closure this year, to move on," Collier said.

Collier said she's planning a trip to visit the inmate who sent the letter.

Grant also said investigators are waiting for the audio tapes from the phone calls the inmate made that are related to the case, and will also being visiting Muskegon.