A Seffner man who used a cell phone jamming device on his daily commute to and from Tampa now faces a $48,000 fine, issued Wednesday by the Federal Communications Commission.

The FCC said Jason R. Humphreys illegally interfered with cellular service along Interstate 4 and disrupted police communications for up to two years.

"This case highlights the danger posed to public safety by use of a single signal jamming device, which can disrupt all wireless and public safety communications in the area," FCC enforcement bureau chief Travis LeBlanc said in a statement.

In 2013, MetroPCS contacted the FCC about its cellphone towers experiencing interference during the morning and evening between Seffner and Tampa. Officials monitored the route and pinpointed Humphreys' sport utility vehicle as the source.

Hillsborough County Sheriff's deputies stopped Humphreys and found that their communication with police dispatch was interrupted as they approached his car. They found a cellphone jammer behind his passenger side seat cover.

Humphreys, a Hillsborough County government employee, told authorities he had been using it for nearly two years to keep people from talking on their cellphones while driving.

The FCC proposed a $48,000 fine, giving Humphreys 30 days to respond by paying in full, requesting an installment plan, or seeking a reduction or cancellation. The FCC said Monday that he did not respond, and that it now "affirms and imposes" the fine.

Using or selling a jammer is against federal law. Jammers block radio communications by preventing devices such as cellphones from establishing and maintaining a connection. They can also interfere with first responder, police and other law enforcement communications, and Wi-Fi-enabled and GPS devices, according to the FCC.