The theft of 100 cylinders containing propane gas in Colorado has prompted an investigation by the FBI, media outlets reported.

The FBI investigation was first reported by KMGH-TV in Denver. Roughly 100 of the cylinders are missing, some since July.

Officials said a single tank, if exploded, could destroy a small building.

KMGH reported that the tanks reported missing in Colorado were not residential units, but larger liquid propane tanks used to power commercial machinery such as forklifts or farm machinery, each containing nearly 8 gallons. Typical residential units carry 1 or 2 gallons. In addition, the larger tanks carry the more concentrated, liquid form of propane.

It isn’t the first time that a propane theft has drawn the attention of federal officials. Land Line reported in June that law-enforcement officials were investigating the disappearance two propane trucks and 15 gas canisters that were stolen during the Memorial Day weekend in San Antonio.

The trucks were found later, but at the time the theft was reported, federal officials publicly stated their concerns about the possible use of the gas by terrorists. FBI Agent-In-Charge Patrick Patterson of San Antonio said at the time of the thefts that the possibility that the propane could be used to create a bomb prompted him to notify the National Joint Terrorism Task Force in Washington and law-enforcement officials in Texas.