Four men remain hospitalized Friday after being injured in a series of explosions at the Hormel Foods Corp. that occurred early Thursday.

Andy Wolf, 33, Chad Swenson, 21, Lee Johnson, 50 and Joe Welke, 54 were taken to Regions Hospital in St. Paul. All are from Austin.

Wolf is in serious condition and Swenson, Johnson and Welke are listed in fair condition. One man, Jeremy McCullough, 27, of Albert Lea, was taken to the Austin Medical Center after explosions, where he was treated and released.

Austin Fire Chief Dan Wilson told reporters this morning, he will hold a press conference this afternoon to reveal the results of the investigation.

According to Wilson and Austin police Capt. Curt Rude, early speculation suggests dust caused the first explosion and a faulty valve may have caused other explosions.

The investigation was labeled "routine" by local fire and police officials, who are still reviewing the notes of firefighters at the scene and their observations, while making a sketch of the room at the Austin flagship plant where the rendering department explosions and fire occurred.

Hormel Foods officials are cooperating with the investigation which is being overseen by the Minnesota State Fire Marshall's Office's own investigators.

The police captain, quoting Wilson, said a "plausible explanation" can be expected later today.

The police captain's own speculation as to the cause of the fire and explosions was called "completely an educated guess."