Arlington, Virginia, officers were investigating shots fired and executing a search warrant when a house exploded.
No deaths have been reported, and the suspect's status in the residence during the explosion is unknown.
Rep. Don Beyer called the explosion "major explosion" and "very, very scary".
A neighboring homeowner described the explosion as "enormous," rocking her house, covering it with broken glass.
Around 4:45 p.m., a flare gun was reported discharged at a Burlington Street home.
Before executing the search warrant, the subject was contacted by phone and loudspeaker.
As police approached the house, the Arlington County Fire Department evacuated neighbors as a precaution.
Police could not verify this account. The neighbor talked anonymously for safety and privacy.