Firefighters have knocked down a fire that tore through a vacant OSU extension building in southwest Medford.

4:25 p.m.Fire investigators suspect the fire that destroyed an unused OSU experiment station today was caused by a person.

All utilities to the multistructure experiment station were shut off several years ago, leading investigators to believe the fire was human-caused, fire investigator Samantha Metheny reported.

A small crew of firefighters remains on scene to monitor hot spots that continue to flare up in the basement, making the former office building unsafe to enter.

Investigators will resume their investigation tomorrow, Metheny said.

12:20 p.m. Firefighters have knocked down a fire that tore through a vacant Oregon State University extension building in southwest Medford.(Updated 12:35 p.m. with details about building.)

Medford Fire-Rescue Battalion Chief Tom McGowan said the fire was reported at 11:26 a.m. and crews arrived to find the building ablaze in the middle of a large field of dry grass. Fire trucks headed down a long dirt road off Kings Highway near its intersection with South Stage Road and ultimately had to lay down 800 feet of hose to attack the fire, he said.

"With current conditions the way they are, our immediate concern was the surrounding area," McGowan said.

Although the building was engulfed by fire, crews "got a good knockdown," he said. Some flames spread to grass and brush, but were quickly stopped.

Some walls and a chimney remain standing amid the smoldering rubble while crews watch for flaring flames. Oregon Department of Forestry crews will monitor the scorched field.

(Updated 12:35 p.m.) Fire investigator Samantha Metheny reported that the abandoned experiment station destroyed by the fire belonged to OSU, but was for sale. There are several other overgrown abandoned buildings on the property.

Metheny found a downed power line in the area and is investigating whether that could have started the fire.

11:50 a.m. Firefighters are responding to a reported barn fire near the intersection of South Stage Road and Kings Highway, near Medford's southwestern city limits.

The fire, which was first reported shortly before 11:30 a.m. sent up a large column of dark gray smoke high into the air.

We'll provide more details as they become available.