DETROIT (AP) -- Michigan transportation officials say they're working with police to determine who hacked into a portable electronic road sign and posted a racial epithet referring to slain Florida teen Trayvon Martin.

Michigan Department of Transportation spokesman Rob Morosi says the sign on the shoulder of Interstate 94 in Detroit alerting motorists to road work was altered sometime late Sunday night or early Monday morning.

The slur was directed at the unarmed black teen fatally shot in February by a neighborhood watch volunteer.

Morosi says authorities were alerted shortly after midnight Monday and restored the original message within an hour.

He says the box in the back of the sign was unlocked, and a keyboard had been removed.

The sign has been taken to a nearby state police post for examination.

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