Portland police say a small explosion that blew out a window of a Southeast Portland apartment building early Monday was the result of someone attempting to manufacture hash oil using butane.

Sgt. Pete Simpson said members of the interagency metro bomb squad were dispatched to the apartment complex in the 17200 block of Southeast Powell Blvd. at about 1 a.m.

While they were heading to the apartment, Simpson said, officers learned from dispatchers that there was a report of 3 people arguing at the apartment and one person punched another in the face; another person had a knife and was allegedly threatening to stab someone.

Neighbors told police they heard a loud explosion at around 12:30 a.m., but did not call 911 until they heard people arguing outside.

He said one person in the apartment was taken by friends and dropped off at a local hospital with burns. A Portland Fire Bureau spokesman said the man was admitted to the Oregon Burn Center at Legacy Emanuel Hospital for treatment.

The process of making hash oil often involves volatile butane gas, which appears to have been the case in Monday's incident.

-- Stuart Tomlinson