(CNN) -- A Charleston, West Virginia, house where six children and two adults perished in a fast-moving fire early Saturday was scheduled to be routinely checked late last month but the inspector was asked to come back at a later time, city officials said.
The two-story rental home had only one working smoke detector, on the first floor, and it was incorrectly positioned, Mayor Danny Jones told reporters hours after the tragedy. It was on the counter, rather than bolted on the ceiling. One other downstairs detector was not working, he said.
"Had we been able to get in that day, and had we seen the fact they did not have the proper number of smoke detectors, we might have saved a lot of lives," Jones said.
All six children were under the age of 8, and they are all related in some way, the city fire department said. Officials said the victims likely died from smoke inhalation.
A seventh child -- the sole surviving child -- was on life support, the mayor said.
The sole surviving adult, a 24-year-old woman, was outside at the time. She was being treated at a hospital, officials said. The woman made the call from a neighbor's house at 7 a.m. ET Saturday, authorities said.
"We do not have any reason to believe this is arson," Jones said. "We believe it started in front on the bottom floor."
The seven children and three adults had spent the night together after a birthday party for one of the adults Friday evening, the fire department said. Jones said several of them apparently lived in the house.
While foul play is not suspected, the Charleston Fire Department is working with police to investigate the case.
Jones said the building inspector arrived at the home on February 28 after the landlord and the tenant had agreed to his visit. But a juvenile whom Jones described as half-asleep told the inspector that the tenant, one of the victims, was out car shopping.
The inspection did not occur and was put back into a long list of residences to be visited. Inspectors check up to 40 homes a day, Jones said.
City Building Inspector George Jarrett told the Charleston Gazette-Mail that rental homes are required to be inspected every two years.
Residents sometimes remove batteries from detectors, officials said. And inspectors are not permitted to order residents to move if they find a problem.
"Most of our inspectors ... are turned away. 'Don't bother us.' To those people who have turned out inspectors away, at least check your smoke detectors," Jones said.
Chief Bob Sharp of the Charleston Fire Department said that this is the most tragic event he has seen with his 26 years with the department.
The dead were identified as Alisha Carter Camp, 26; Alex Seal, an adult, age unknown; Keahna Camp, 8; Jeremiah Camp, 3; Elijah Scott, 3; Emanuel Jones, 18 months; and Kiki and Gigi, appoximately 3 years old, last names not known.
Authorities didn't immediately know whether all the people in the house lived there.
"One of the messages we get out of this tragedy is we need these inspectors," Jones said.
Downstairs areas need at least one smoke detector. Every bedroom should have a detector, as should hallways next to the bedroom, officials said.
CNN's Michael Martinez, Phil Gast, Elwyn Lopez and Kara Devlin contributed to this report.