Half a dozen people were displaced and more than 15 cats are unaccounted for following a fire in Woodstock early Wednesday.

The Woodstock Fire/Rescue District was called to the 600 block of Clay Street just after 1 a.m. Wednesday, Woodstock Fire/Rescue District spokesperson Alex Vucha said.

“Crews arrived and located a two-story older wood frame home with heavy fire showing from second floor windows. Firefighters stretched multiple hose lines and made entry to the structure, encountering heavily cluttered conditions and a narrow staircase that limited access while attempting to reach the fire in the upstairs apartment,” Vucha said.

Everyone inside the building, which had four individual apartments, safely exited before emergency personnel arrived.

Water was on the fire within minutes of crews arriving, but crews upgraded the call because of the heavy fire conditions and unknown extension throughout the building, Vucha said.

“Firefighters operated on the roof to perform vertical ventilation due to fire involvement in the attic space, while interior crews continued fire attack,” Vucha said.

Most of the fire was contained to an upper front unit, whose contents are considered a complete loss, Vucha said. Smoke and water damage extended throughout the structure, though some items in other units were salvageable, Vucha said.

But a large number of cats, described as more than 15, were reported to be unaccounted for, officials said.

The American Red Cross is assisting displaced residents. Six people were affected.

Final crews cleared the scene shortly after 4 a.m. and the Woodstock Fire/Rescue District is investigating the cause.

“The Woodstock Fire/Rescue District would like to thank all responding agencies, both on scene and those providing change of quarters coverage, along with the Woodstock Police Department and our dispatchers for their assistance during the incident,” Vucha said.