LOS ANGELES — Alleged members of a Southern California ring that used a device to cheat state smog inspections are facing federal charges, officials announced Thursday.

An indictment unsealed Thursday in Sacramento federal court charges the defendants with allegedly having manufactured, distributed and used "OBDNators" to cheat smog checks across the state, according to the U.S. Department of Justice.

Court documents allege that between October 2015 and last month, the defendants participated in a conspiracy to cause polluting vehicles to pass California's smog checks. Smog checks are typically performed by plugging smog inspection equipment, known as a Data Acquisition Device, into a vehicle's On-Board Diagnostics port. To cheat smog tests, the conspirators plugged the smog inspection equipment into the OBDNator device instead, the indictment alleges.

The OBDNator would then make it look like a vehicle had passed the smog check regardless of the true condition of a vehicle's emission control system. While the defendants' roles in the conspiracy varied, all of them used the OBDNator devices, according to the DOJ.

"For many years, California's Smog Check Program has successfully reduced the amount of pollution in the air we breathe by identifying polluting vehicles and requiring them to be repaired or retired," U.S. Attorney Phillip A. Talbert said in a statement.

"The developer and users of the OBDNator smog check cheating devices who are charged in the indictment ... polluted the air we breathe for their own profit and harmed the health of Californians. Anyone who may be tempted to utilize a device to cheat on smog checks should consider that they too could face federal criminal charges and possible prison time."

According to court documents, Los Angeles-area smog station owner Hossam "Sam" Hemdan, 54, of Hawthorne, developed the OBDNator device and its accompanying software program. He allegedly sold and distributed the devices for as much as $18,000, the DOJ alleges.

After plugging the smog inspection equipment into the OBDNator, the alleged conspirators would use the device to convey false smog check information to the California Bureau of Automotive Repair. The OBDNator provided the Vehicle Identification Number and passing "answers" to the smog inspection equipment's queries in the exact format that a passing vehicle of the same make, model and year would provide, court papers show.

Federal prosecutors allege that in order to provide the false answers, the defendants and others maintained collections of "clean" vehicle profiles that they would use to make it look like other, different vehicles had passed.

The latest version of the OBDNator could pass a vehicle without that vehicle even being present at the smog station. During the conspiracy, some of the defendants organized classes to teach how to use the OBDNator and communicated through group chats about how to avoid detection by authorities, the DOJ contends.

Hemdan is charged with conspiracy and making false statements pursuant to the Clean Air Act, along with:

• Javier Salguero, 47, of Inglewood, owned and controlled several smog shops, including one in Bell and two in Maywood;
• Oscar Gomez, 36, of Rancho Cucamonga, ran a school for automotive technicians in Rancho Cucamonga;
• Guillermo Tovar, 35, of Fontana, worked at multiple smog stations;
• Arwa Harb, 53, of Redondo Beach, owned and controlled smog stations, including one in Wilmington and one in South Gate;
• Thong Truong, 40, of San Jose, owned and controlled smog stations, including two in Long Beach; and
• Michael Nguyen, 38, of National City, operated out of a smog station in Spring Valley.

The following defendants are charged with conspiracy:

• Yehia Harb, 36, of Hawthorne, owned and controlled a smog shop that was formerly in Venice and presently is in Hawthorne;
• Khaled Hamdan, 31, of Hawthorne, worked at businesses owned by Hemdan;
• Jeremy Earls, 37, of Lakewood, owned and controlled smog stations, including two in Long Beach; and
• Nas Meshal, 30, of La Palma.