Minnesota state troopers cited 678 drivers for violating the hands-free law during its first week in force.

The law prohibits holding a cellphone while driving — to prevent motorists from being further distracted by the devices.

The highest number of citations — almost 300 — were written in Hennepin County. Troopers issued 79 citations in Ramsey County and 60 in Dakota County.

Before the law went into effect Aug. 1, it was already illegal in Minnesota for drivers to send text messages and emails while driving, or use the internet. Phone calls were permitted as long as the driver wasn’t distracted.

Now drivers must switch to hands-free or voice-activated mode. Emergency calls are exempt from the law.

Drivers who violate the law face a $50 fine in the first instance, but that increases to $275 for subsequent violations.