One person died and 36 people were left homeless Sunday in an apartment fire that started shortly before 7 a.m. in a building that was facing condemnation by the city of Everett, city spokeswoman Meghan Pembroke said.

The building owner was working on making improvements to the stairwell of the structure in the 1800 block of Hewitt Avenue, making sure each floor of the 1923 building had doors and other upgrades.

The work was supposed to be done by Dec. 20 or the tenants would have to move. While the owner was planning to do the upgrades, the work had not been done yet, Pembroke said.

Now the owner faces a separate condemnation action because of the fire damage, she said.

As Everett firefighters were fighting the blaze they discovered a body inside the building. Aaron Snell, spokesman for the Everett Police Department, said no information about the victim’s gender or identity would be released yet. The Snohomish County Medical Examiner’s Office will conduct an autopsy.

No one else was injured.

Arson investigators with the Everett Fire Department are looking into the cause of the fire.

During the blaze, Hewitt Avenue between Oakes and Wetmore avenues was closed for two hours while firefighters and police were at the scene.

The Red Cross set up a headquarters at Central Lutheran Church, where 17 of those left homeless by the fire were given shelter and food. The others who lost their homes were presumed to have family or friends’ homes to go to, said Chuck Morrison, regional chapter executive of the Red Cross.

“It’s really bad when this happens at Christmastime,’’ he said.

The apartment building will remain off-limits to residents until detectives finish their investigation and turn it over to the owner and manager. Then repairs will have to be completed before anyone will be allowed to live there, Snell said.

Anyone with information about the fire is asked to contact the Everett Police Department tip line at 425-257-8450 or call 911.

Nancy Bartley: nbartley@seattletimes.com or 206-464-8522