No injuries were reported after a South Side explosion rumbled through St. Joseph early Friday morning.

City and county law enforcement officers were called to Ag Processing on the Stockyards Expressway around 3:19 a.m. St. Joseph Police Capt. Matt Rock said an external hydrogen holding tank exploded.

Twenty-five to 30 employees were at the plant at the time of the explosion, with 10 to 15 in the area of the explosion. But no injuries were reported.

City public relations officer Mary Robertson confirmed the incident details at a press conference later at City Hall.

St. Joseph Fire Chief Mike Dalsing said he believed no one was injured because the explosion occurred outside, on the south side of the facility and, because hydrogen is a light gas, the explosion rose in the air instead of spreading out.

Also, he said AGP has been fully cooperative with advanced emergency planning. When firefighters arrived on the scene, plant officials were able to account for all employees and direct emergency responders to the exact location of the explosion.

Mr. Dalsing also said the tank was one of six hydrogen storage tanks. The explosion in the lone tank caused fires throughout the tank holding area, but employees and firefighters were able to use nitrogen to purge all six tanks and avoid further explosions.

AGP had just taken delivery of a supply of hydrogen prior to the incident, but Mr. Dalsing declined to connect the delivery with the explosion. He did say that the explosion's debris field extended 70 to 80 feet to the south of the holding tank. To the north, debris was found as far as 180 feet away. Another building at AGP suffered some structural damage, including bent I-beams.