Authorities are investigating a string of drive-thru robberies at Houston-area McDonald's restaurants.  According Houston police and the Montgomery County Sheriff's Office, five different McDonald's drive-thru windows have been targeted by armed robbers in the last two months.

The most recent happened Thursday night at the McDonald's on 6615 Tidwell.  Police said two masked men approached the drive-thru and demand the employee open the window.  She refused and one of the men fired his shotgun through the glass.  The young woman was hit on the arm and shoulder but will recover.

Earlier that same day, police said a McDonald's on Beltway 8 and Bammel Road was targeted.  According to police, a woman pulled up to the drive-thru pretending to be a customer.  That's when a man with a gun jumped out of the passenger seat and rushed toward the window.  The frightened employee ran into the freezer for safety.

In the Panther Creek Shopping Center in the Woodlands on Oct. 4, two men are accused of firing shots at a customer after making their way into the restaurant via the drive-thru window.

Just a week later, another drive-thru robbery occurred at the McDonald's on 6730 Woodlands Parkway.  Deputies said three men wearing masks and pointing guns also forced their way through the window.

Once inside, the men terrorized the employees before making off with drawers full of cash.  In this case. police were able to make one arrest. Justin Harris, 20, was charged with aggravated robbery.

Finally on Nov. 22, three armed men shot out the drive-thru window and climbed into the McDonald's off 249 near FM 1960.  Shots were fired but no one was hurt.

Police said drive-thrus can be desirable targets because fast food restaurants mostly deal in cash, they're open late and the cash register is often next to the window.

Houston police said they have no evidence the crimes are connected, but they are keep an eye out for the possibility.