Washington, Nov 16 (IANS/RIA Novosti): Pranksters in the US are finding ways to alter messages on electronic traffic signs, including one hacker in the state of California who advised travellers to smoke marijuana and proceed with caution while driving due to a loose gorilla.

"It is rather difficult to get into them," Tony Firenzi, senior engineer for the Placer County Water Agency (PCWA), told The Sacramento Bee about the electronic sign that was supposed to notify drivers that a road in the northern California town of Loomis would be closed for a PCWA pipeline construction project.

"There is some kind of electronic equipment that is needed to access the computerized system," Firenzi added. "There must be some pretty savvy people out there who were able to bypass all of that."

It took some technical skill and a keyboard for the unknown hacker to change the messages on the traffic sign that were seen on three separate nights beginning last week, the Bee reported.

The first message recommended that people "Smoke Weed Everyday", followed by a second message that said "Caution Loose Gorilla!" and a third sign was reported by the Bee to be profane.

Other instances of highway sign hacking have occurred recently in the northeastern US in the state of Maine with a sign that said, "Warning Zombies Ahead!" and another sign was discovered in Massachusetts that read, "Seek Alternate Route, Zombies Ahead."