Prince Rupert is planning to celebrate its 100th birthday in March by unearthing a time capsule that was buried 40 years ago.

But there's a problem: Officials in the north coast B.C. city don't know where it is.

"It's a real mystery," Joan Cameron, executive assistant to the mayor, told in a phone interview.

Officials know this much: It's buried somewhere in a small park near the hospital.

The city archive has photographs showing local officials burying the capsule -- a four-foot-long cylinder that resembles a propane tank -- with several children looking on. Prince Rupert harbour can be seen in the background.

Problem is no one bothered to place a permanent marker there.

Citizens have tried locating the time capsule with metal detectors but so far have been unable to find it, Cameron said.

The capsule contains a variety of items from local citizens: canned salmon; catalogues; newspapers; a centennial dollar; written messages and predictions of what 2010 would be like from politicians, including Premier William A.C. Bennett, MP Frank Howard and Mayor Peter Lester.

Cameron said the local heritage society's members started looking for the time capsule a few months ago, and then turned to the city for help when they couldn't find it. 

The city is now appealing to the public for help.

However, Cameron emphasized that the city is not interested in people digging holes in the park.