Nevada ? Prosecutors filed 12 counts of first-degree murder Thursday against a woman they say started a deadly hotel blaze by setting a mattress on fire after a dispute with a fellow tenant.

Valerie Moore, 47, a convicted murderer who was paroled a year ago, was arrested the morning after the Oct. 31 fire but had been held on a parole violation while authorities searched for bodies – a process that took until Wednesday because the gutted building was so hazardous.

The fire at the 84-year-old, $150-a-week Mizpah Hotel was Reno’s deadliest, killing 12 people and injuring 31.

As many as 83 tenants were in the Mizpah Hotel when the fire broke out, police said. Many were rescued by firefighters on ladders.