TOPSHAM (AP) – The search for a Topsham teenager last seen leaving a party in downtown Brunswick nearly a week ago is focusing on the rain-swollen Androscoggin River.

A Maine Warden Service airplane and Maine State Police detectives joined Thursday in the search for Michael Nord, a 17-year-old student at Mount Ararat High School.

“We are considering this to be suspicious because we don’t know why he is missing. There is no history of him ever running away from home. It’s not something he would normally do,” Topsham Police Chief Tim Young said. “No one has seen or heard from him since (Friday night), which is very unusual.”

Investigators theorize that Nord attempted to walk the several miles from the Gilman Avenue party to his home, which would have led him to use one of the five pedestrian river crossings between Brunswick and Topsham.

The plane flew over the Androscoggin on Thursday afternoon, but the spotter found nothing. The search was to resume Friday.

“We don’t know where he went after he left Gilman Avenue. All we can do is put him with friends until early Saturday morning,” Young said. “What concerns us is the river between Brunswick and Topsham.”

Late Thursday afternoon, the surging Androscoggin was rushing under the swinging foot bridge between Topsham and Brunswick on its way downriver to a hydroelectric dam. Water flows over the dam, past the Bowdoin Mill complex, on its way to Merrymeeting Bay.

Police said the river’s high level made it too dangerous for civilians to conduct a search of the river banks, though several had volunteered to help.

“Right now, the river is surging way too high. We can’t take a chance that someone might fall in,” said Topsham Police Lt. Christopher Lewis.