They know where it started, just not how.

Investigators don't know what caused a Christmas Day fire at a downtown Minneapolis homeless shelter that displaced hundreds of people, fire investigators said Thursday.

The cause of the fire at the Francis Drake Hotel  remains undetermined after an investigation. Fire investigators said the fire started in unit 244, but they could not identify a specific cause. 

The Minneapolis Fire Department said the investigation remains open and the cause of the fire could be changed later if more information becomes available. 

The fire broke out at 3 a.m. on Christmas Day. Around 250 people were displaced. Three people were injured and taken to HCMC.

Many of the residents who were forced out because of the fire damage have been living in churches and a hotel.

The apartment building mostly served as temporary housing for homeless people. 

The hotel was built in 1926 as a luxury hotel with 146 rooms. Hennepin County converted it to temporary housing for when there's no room at other homeless shelters.