Nearly nine months after General Motors began recalling millions of its cars for dangerously defective ignition switches, almost half of the vehicles still have not been fixed.

With the repairs dragging on, hundreds of thousands of cars with the GM ignition switch defect remain on the road. As of Aug. 21, only one-third had been fixed.

A spokesman for the automaker said it was increasing its outreach to owners through social media and a new call center staffed with 72 employees dedicated to contacting those who have not scheduled repairs.

General Motors is sending Facebook messages to track down more than a million car owners who still haven’t had potentially fatal GM ignition switch defect fixed.

There has been heavy publicity surrounding the recall, including thousands of news stories and five congressional hearings, but it seems that the message is still not getting through. Despite recall letters that bluntly warn that the GM ignition switch defect can lead to injury and even death, only about 1.16 million of the 2.36 million affected vehicles still on the road have been brought in for repairs. About one-third of those who have not had the repairs done are people with children, while one-fifth are young people without children.

As a result, GM has been forced to go beyond the usual ominous-sounding recall letters. It has sent out Facebook messages and made phone calls to owners of the cars, mainly Chevrolet Cobalts and Saturn Ions. General Motors’ CEO Mary Barra has even sent a personal letter urging people to get the GM ignition switches replaced.

But owners who requested repairs months ago have been waiting, with dealers managing wait-lists and dozens of drivers writing to federal regulators in recent weeks asking why it was taking so long. Some of them are also raising safety concerns about the drawn-out timetable.

Because the recalled cars are no longer produced, parts supplier Delphi Automotive had to bring in machinery to start manufacturing replacement switches. Repairs finally began in April when the replacement switches started to arrive at dealers. Recently, GM announced that Delphi had made enough to fix all the cars.

GM’s efforts to reach people are part of an agreement that ended a federal investigation into why the automaker failed to promptly disclose the switch problem. GM announced in February and March that it was recalling the cars after taking more than a decade to disclose the defect, now linked to at least two dozen deaths.

It explained that the GM ignition switches can wear from heavy, dangling keys. If the key chains are bumped or if the car is driven on rough surfaces, the switches can suddenly change from the run position to accessory or off. This cuts off power-assisted steering and brakes and can cause drivers to lose control.

The airbags also may not inflate in a crash and protect the driver and passengers. GM is urging people not to put anything on their key rings until the switches are replaced.

It is not unusual for some car owners to ignore recall notices. The average completion rate 1.5 years after a recall begins is 75 percent, according to federal safety regulators.