Authorities are warning motorists in parts of Iowa about a series of sexual assaults that have occurred along rural roads.

After receiving several reports of assaults along rural roads in Black Hawk, Linn and Tama counties, the Black Hawk County Sheriff's Office is urging motorists to use caution when driving along rural roads in northeastern Iowa.

“Please report suspicious activity to law enforcement, and use your best judgement and caution when encountering suspicious persons,” sheriff officials said in a Facebook post.

The latest case of sexual assault occurred on Aug. 25, when a woman reported that she was flagged down by a man on a rural road near Bertram, KCCI reported.

When the woman got out of her car to help the man, he pushed her against his vehicle and sexually assaulted her, investigators said.

Iowa authorities are urging motorists to report anyone they see stopped along a roadway.