The Seattle Fire Department (SFD) evacuated an apartment building on 1st Avenue North on Wednesday morning after reports of an explosion. 

SFD said one person is in serious condition. There are no active fires in the building. 

SFD said:

"911 calls within the building report hearing an explosion within a basement unit. We are evacuating the building as a safety precaution. HazMat crews are also responding." 

SFD established a 1-block perimeter around the building as fire and law enforcement personnel investigated the incident. 

KOMO News' Kelly Koopmans said this: 

Another KOMO reporter said police are trying to "diffuse a device."  

"Stuck in my apt while the bomb squad investigates an explosion across the street," said a person who lives down the street from the incident area. 

*Developing