HULL, Iowa -- The Humane Society of the United States is offering a reward of up to $2,500 for information leading to the arrest and conviction of the person or persons responsible for an act of vandalism that killed thousands of pigs last week at a hog confinement near Hull.

Carol Griglione, the organization's Iowa director, said in a statement released Thursday that whoever intentionally suffocated the 3,800 pigs by turning off the confinement's airflow and alarm systems needs to held accountable.

"This kind of intentional cruelty to animals is unacceptable and the persons responsible for these senseless deaths need to face stern penalties," she said.

Sioux County Sheriff Dan Altena said Thursday that a Des Moines-based organization that supports farmers also contacted him about offering a reward for an arrest in the case. Altena said investigators are looking at "people of interest," but he said they have no suspects at this time.

Authorities say someone entered the facility, at 2739 Highway 75, and intentionally turned off the confinement's airflow and alarm systems sometime during the overnight hours Thursday, causing all of the pigs to suffocate.

At 10:30 a.m. Nov. 13, confinement owner Todd Hasche, of rural Rock Rapids, Iowa, called police and reported that all of the feeder pigs at the facility were dead and that someone had tampered with the confinement's airflow system.

Hasche, who owns three hog confinements, told the Journal on Monday that the main breakers in the barn and a stand-by generator were turned off and the alarm system was disabled.

The 50- to 60-pound pigs, owned by Sioux Feed Company, were ready to be shipped off Friday afternoon. Instead, Hasche and his friends and neighbors spent three hours removing their carcasses from the barn. The pigs were turned over to a rendering business, which took them to a rendering plant where they will be recycled into livestock feed.

The loss of the pigs, which were insured according to Sioux Feed Company, is estimated at more than $200,000.