PORTLAND – Portland police are seeking the public’s help in their search for a Harvard Business School student who disappeared after spending a night out on the town with two of his classmates.

Nathan G. Bihlmaier, 31, of Cambridge, Mass., came to Portland for the weekend with two friends to celebrate their graduation, scheduled for Thursday.

Portland police said the three men were partying Saturday night in the Old Port area when Bihlmaier decided to leave Ri Ra, an Irish Pub on Commercial Street, on his own just before the 1 a.m. closing time. When Bihlmaier’s classmates – also from Massachusetts — looked for him, he couldn’t be found.

They returned to their hotel room, assuming that Bihlmaier would eventually show up. But when he did not return by noon Sunday, the classmates notified police that he was missing.

“It’s an unusual one,” said Lt. Gary Hutcheson. “He is a well-established individual from a strong family. He has a wife who is expecting their first child. There is no reason he would (purposely) go missing.”

On Sunday, police used cellphone transmission records to track Bihlmaier’s movements. He remained within the Old Port, but his phone battery apparently died about 40 minutes after he left the bar, Hutcheson said.

Police called in their dive team to search the water around the Casco Bay Lines ferry terminal Sunday afternoon. Divers found no evidence that Bihlmaier had fallen into the harbor.

“We’re kind of at a loss right now,” Hutcheson said.

Police released a photograph of Bihlmaier with his wife, Nancy Ho Bihlmaier. The photo accompanied a news release that asks the public to contact police at 874-8479 with any information on Nathan Bihlmaier’s whereabouts.

His wife did not initially make the trip to Portland, but after learning her husband was missing, she arrived later on Sunday, Hutcheson said.

He said the fact that the three classmates chose Portland instead of Boston for celebrating their graduation is not uncommon.

“The Old Port is pretty well known throughout New England. If you are within driving distance, why not come here?” he said.

Staff Writer Dennis Hoey can be contacted at 791-6365 or at:

dhoey@pressherald.com