Hackers suspected to have ties to Iran may have infiltrated computerized fuel monitoring systems at gas stations across the United States, according to CNN on Friday.

The report said the suspected cyber intrusions targeted automatic tank gauge systems, or ATGs, which are used to track fuel levels and detect leaks in underground storage tanks at gas stations.

The CNN report suggested that federal investigators think the activity was carried out by hackers linked to Iran but officials have not publicly connected the operation to a specific branch of the Iranian government.

U.S. officials told CNN that some of the systems had been connected to the internet without password protection, potentially allowing hackers to access and manipulate digital readings and display settings. 

Investigators warned that falsified readings could hide leaks or create other safety problems.