By David DeKok

HARRISBURG, Pa. (Reuters) - Philadelphia police said on Monday they will not investigate the weekend vandalism that ended an experimental robot's attempted hitchhiking trip across the United States unless the Canadian universities that own it file a criminal complaint.

The child-sized robot, named hitchBOT, had safely hitchhiked across Canada and through parts of Europe.

But its trip from Boston to San Francisco ended abruptly on Saturday in a Philadelphia alley, where it was found with its head removed.

"We can't do anything without a complaint being filed," Philadelphia Police spokeswoman Leeloni Palmiero. "If they did, we would absolutely investigate."

The robot's owners said they have no interest in mounting a criminal prosecution.

"We wish to remember the good times, and we encourage hitchBOT's friends and family to do the same,” the team behind the project said in a statement posted on the hitchBOT website. (

"Sometimes bad things happen to good robots."

HitchBOT was the brainchild of professors David Harris Smith of McMaster University in Hamilton, Ontario, and Frauke Zeller at Ryerson University in Toronto.

Smith said on Monday that the team has not decided whether to rebuild the robot. He said the material cost of the original hitchBOT was only about C$2,500 ($1,900 U.S.), but that "hundreds of hours of work" would be necessary for a new model.

"There is a lot of testing to make sure everything will work," he said.

HitchBOT left Salem, Massachusetts, on July 17 and made stops in Boston and New York City before traveling to Philadelphia. The team that built him intended for hitchBOT to hitch-hike to San Francisco, with stops at places like Mount Rushmore and the Grand Canyon.

It was 3 feet (91 cm) tall and weighed 25 pounds (11 kg), according to Ryerson University. The robot could not move and was dependent on motorists stopping and lifting it into their vehicles.

In the summer of 2014, hitchBOT crossed Canada, from Halifax, Nova Scotia to Victoria, British Columbia in 19 separate rides lasting 26 days. It has also hitchhiked through Germany and the Netherlands.

(Editing by Scott Malone and Eric Walsh)