An unconventional love note set off a bomb scare in Philadelphia on Monday.

Police, fire units and the bomb squad were called to an Amtrak station in the heart of the city after workers spotted a suspicious device.

It turned out to be a battery-operated timer rigged to make a string of lights flash the message "I Love You Sonia."

Officials are not taking the incident lightly.

Amtrak is increasing security and police have launched a full investigation to find the person behind the device.