Police investigating explosion in Edmonds

EDMONDS, Wash. - UPDATE: Investigators determined the explosion was a plastic pop bottle set off by an Edmonds man who was later arested. 

Highway 99 has reopened. 

ORIGINAL STORY: 

Police in Edmonds are investigating an explosion that has closed a portion of Highway 99.

Edmonds Police said on Twitter that there was an explosion of some kind, and remnants from "one crude device" were found in the area. Washington State Patrol has been called in to assist. 

Highway 99 is shut down between 238th and 234th streets, and 236th is closed from Highway 99 to 76th Street. 

No one was injured, and investigators say they haven't found any property damage. 

Police have not released any additional information on what kind of explosive was used, or when and where exactly the explosion happened.