Like thousands of family members all over the planet, hundreds of Canadians spent yet another agonizing day waiting to hear whether they had lost a loved one to Tuesday's morning of destruction.

As of yesterday, between 50 and 100 Canadians were unaccounted for. The estimate is based on information received from more than 8,300 calls over the past three days, said Oussamah Tamim, a spokesman with the Department of Foreign Affairs. "I should stress . . . these numbers are probably going to change," Mr. Tamim said.

Wednesday, for example, Foreign Affairs had reported that three Canadians were confirmed to have died on the two hijacked United Airlines flights. But yesterday, Mr. Tamim said one of the three was not a Canadian citizen, although they did live in Canada.

Information is not yet available as to whether any Canadians were on board the two other planes deliberately destroyed in Tuesday's attacks. And there has been no word about any Canadians pulled from the fallen World Trade Center.

One of those missing is Ralph Gerhardt, the younger son of Toronto hotelier Hans Gerhardt and his wife Helga. Joe Ebner, general manager of Toronto's Delta Chelsea Hotel and a long-time friend of the family, said Mr. Gerhardt, who is in his 20s, was at work in the World Trade Center when the planes rammed the building.

Mr. Ebner said that Mr. Gerhardt had telephoned his family afterward and said he was all right and that he was going to find his fiancée. "I heard that he told them he was going to look for her on a higher floor and that they would come out together."

Mr. Gerhardt's friend Geoff Eby told CBC Newsworld yesterday that his friend told his mother in that same call, "There's been a bomb in the building. I'm just calling to let you know I'm okay, but I've got to get out of here. I've got to go now."

Since then, the Gerhardts have heard nothing from their son and Mr. Ebner said Hans and Helga Gerhardt left Wednesday for New York, "to be closer to the situation.

"Just a few days ago Hans was talking proudly about his son Ralph . . . saying that he was doing really well with his job at a bond-trading firm and working at the World Trade Center," he said.

Many desperate family and friends reached out over the Internet, creating Web sites where they are appealing publicly for information about loved ones.

Online survivor lists have become part of an anguished routine for relatives clinging to the hope that on the next round of checks a loved one's name will appear. One such list, World Trade Center Survivor Data Base, posted through http://www.ny.com, contains more than 17,600 names and is billed as being updated every half an hour. There is no way, unfortunately, to verify information on the list.

"We go through all these Internet sites, we call the hospital numbers and then when we get to the end we start again," said Toronto's Erica Basnicki, whose father Ken happened to be at the World Trade Center on business Tuesday.