Residents in Milwaukie were finally allowed out of their homes Thursday night after an ammonia leak sent three people to the hospital and snarled traffic on Mcloughlin Boulevard for nearly six hours.

It all started around 3:00 p.m. after some sort of explosion at Americold Storage at 9501 SE Mcloughlin.

Americold Storage is a cold storage company that uses ammonia as its refrigerant.

Three employees from Americold Storage were taken to the hospital, according to Lt. John Hopkins with the Clackamas Fire Department

Hopkins said the employees needed decontamination and treatment for injuries. A bicyclist riding in the area was also transported to a local hospital.

The building was evacuated but there were also three workers on the roof that needed to be brought dowen by ladder.

Hopkins said the Oregon Liquor Control Commission building next door was also evacuated.

Using a reverse 911 system, emergency crews called residents within a one-mile radius of the scene and instructed them to stay indoors until the cleanup efforts were complete. Residents were allowed to leave their homes again shortly before 9:00 p.m.

Mcloughlin was closed during the duration of the incident.

Hopkins said the cause of the explosion which caused the leak was still under investigation.