Motorist Robbed After Parking Car : Crime: Police say the hold-up of a Mercedes- Benz driver was the 15th follow-home crime this month.

Thieves struck again late Wednesday in the northwestern San Fernando Valley, bringing to 15 the total number of so-called follow-home robberies in the area this month, police said.

In the latest incident, a man robbed a North Hills woman near midnight after she parked her Mercedes-Benz in the garage of her home in the 15800 block of Plummer Street, police said.

The man escaped in a waiting car with the woman’s purse and $537.

But police say the robbery does not appear to be the work of two groups suspected in several of the 10 robberies reported in the Los Angeles Police Department’s Devonshire Division this month.

In the West Valley, there have been four follow-home robberies reported this month, Lt. George Rock said. One follow-home robbery was also reported in the northeast Valley’s Foothill Division this month.

Authorities are also investigating whether the same culprits are linked to five additional follow-home robberies that took place between August and November in the northwestern Valley.

Police know that at least some of the crimes are related because a purse stolen in one of the West Valley robberies was recovered at the scene of a second follow-home robbery in the Devonshire Division on the same night.

In that incident, a 52-year-old man was shot in the chest as he tried to retrieve valuables stolen at gunpoint from his family when they arrived home in the 17100 block of Prairie Avenue.

Police Lt. Bob Normandy said one group is suspected of committing nine of the crimes, in which two to four bandits pointed a gun at their victims and ordered them to hand over valuables. Another group is suspected of committing five additional robberies involving mostly Asian victims that took place north of the Simi Valley Freeway.

Police say that no suspects have been identified. Officers from the LAPD’s elite Metropolitan Division continue to assist in the investigation, and Neighborhood Watch groups have been alerted to the crimes.

Detectives have been unable to determine how the robbers picked their victims, who were followed from a variety of locations.

“Police are baffled,” Normandy said.

The woman who was robbed Wednesday, for example, told police she did not notice anyone following her from her job Downtown to her North Hills home. Other victims were on their way home from shopping malls and, in at least one case, a Ventura Boulevard restaurant.

Last week four members of a Van Nuys family were tied up for two hours while two men ransacked their house. And a Granada Hills man was shot in the shoulder when he fled from robbers.