The FBI and the US National Highway Traffic Safety Administration have added their voices to growing concerns about the risk of cars being hacked.

In an advisory note it warns the public to be aware of "cybersecurity threats" related to connected vehicles.

Last year Fiat Chrysler recalled 1.4 million US vehicles after security researchers remotely controlled a Jeep.

People who suspect their car has been hacked were told to get in contact with the FBI.

The public service announcement laid out the issues and dangers of car hacking.

"Modern motor vehicles often include new connected vehicle technologies that aim to provide benefits such as added safety features, improved fuel economy and greater overall convenience," it read.

"With this increased connectivity, it is important that consumers and manufacturers maintain awareness of potential cybersecurity threats."

The FBI also warned that criminals may latch on to online vehicle software updates by sending out fake messages that trick users into “opening attachments containing malicious software".

Both General Motors and BMW have recently issued security updates to mitigate the risk of remote attacks that would have allowed hackers to open doors and, in the case of GM, start the engine.

Fiat Chrysler was forced to recall millions of vehicles after Wired magazine demonstrated how hackers could remotely take control of car functions, including steering and brakes.

However, there has not yet been a real-world example of such hacking.