COLLINSVILLE, Ill. – Electronic message boards meant to warn motorists of possible trouble on the road are being taken over by pranksters putting drivers on notice about everything from Nazi zombies to raptors. And highway safety officials aren’t amused.

The latest breach came during Tuesday morning’s rush hour, when hackers changed a sign along southbound Interstate 255 near St. Louis to read, “DAILY LANE CLOSURES DUE TO ZOMBIES.”

On Monday in Indiana’s Hamilton County, the electronic message on a sign in Carmel’s construction zone warned drivers of “RAPTORS AHEAD – CAUTION.” Just days earlier, “NAZI ZOMBIES! RUN!!!” and “ZOMBIES IN AREA! RUN” flashed on electronic signs at a busy Austin intersection, just west of the University of Texas campus.

As an Illinois Department of Transportation supervisory field engineer, Joe Gasaway worries that such pranks – while raising eyebrows and prompting chuckles among some motorists – may dangerously distract drivers from heeding legitimate hazards down the road. Tuesday’s real warning near here was meant to ensure safety of crews replacing guardrails.

“We understood it was a hoax, but at the same time those boards are there for a reason,” Gasaway said of the zombie warning. “We don’t want (drivers) being distracted by a funny sign.”

How exactly pranksters did it remains unclear. Austin Public Works spokeswoman Sara Hartley suspected the hackers there cut a padlock to get into the signs’ computers. Gasaway believes the Illinois sign was changed remotely.

But some Web sites encourage the mischief, in some cases publishing a step-by-step lesson titled “How to Hack an Electronic Road Sign.”

Such instructions appear on Jalopnik.com. It’s an auto blog whose editor-in-chief, Ray Wert, considers the postings borrowed from another Web site as a benevolent bid to encourage traffic-safety officials to take securing the signs more seriously.

Jalopnik also urges its guests not to hack into electronic road signs using the information on the Web site, which Wert said has a viewership of 2.6 million a month.

“Hacking generally is about showing where there are holes in security systems, and I think this is a great example of that,” Wert told The Associated Press by telephone Wednesday. “This is an issue that needs to be confronted by traffic safety and transportation officials.”