LEWISTON – The investigation into an explosion on Main Street has found that Northern Utilities was not in violation of gas-line rules when a leak destroyed two buildings on Jan. 12.

The blast and a subsequent fire demolished Lewiston Radiator Works and the former Hotel Holly. Five people were injured.

In a report issued this week, the Maine Public Utilities Commission found that Northern Utilities, a natural gas supplier, had properly operated and maintained its pipeline where the leak occurred.

According to the PUC report, a 6-inch underground pipe broke in two stages. The bottom part fractured about six months before the explosion because of sunken soil under the pipe, possibly as a result of earthquakes the previous summer.

The top part of the pipe was fractured by an underground shock wave from the explosion.

The blast was caused by gas leaking from the cracked pipe and moving horizontally because of deep frost. The leaking gas followed the path of least resistance: to a disconnected service line in the foundation of the former hotel.

Although the PUC found that Northern Utilities had not violated any state or federal regulations, the agency made several recommendations for improving performance and public safety.

The recommendations were made with the intent of improving patrolling, record-keeping and reporting procedures, said Gary Farmer, gas safety manager for the PUC. “These improvements would not have prevented the accident since human error was not a cause,” he said.

People are invited to file comments on the report with the PUC by June 25.