Maine shooting manhunt: River trawled in search for suspect

The search for shooting suspect Robert Card continues on Friday.

Police are searching a river as they hunt the suspect in a mass shooting at a restaurant and bowling alley in Maine on Wednesday.

Divers, helicopters and shoreline patrols will scour the Androscoggin River, Maine Safety Commissioner Mike Sauschuk said.

He emphasised the hunt for US Army reservist Robert Card is not isolated to that area.

The attack in the city of Lewiston left 18 people dead and 13 wounded.

"We are on 24/7 and we will be until the suspect in this case is brought to justice," Mr Sauschuk told reporters on Friday.

Authorities have not released the names of the victims, but the state's medical examiner's office said all have been identified. Those killed in the attack ranged in age from 14 to 76, the Associated Press reported.

Thus far, investigators have given no indication that they have uncovered a solid lead in the manhunt. They did reveal, however, that a note had been found at a property linked to the suspect.

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Investigators did not elaborate, but two unnamed law enforcement officials told the Associated Press it was a suicide note that did not provide any specific motive for the shooting. It was addressed to his son. The suspect's mobile phone was also discovered at the property.

Authorities found the suspect's white Subaru Outback at a boat ramp in the nearby town of Lisbon, beside the Androscoggin River.

Mr Sauschuk said they found additional evidence in the car, without providing further details.

"I'm not saying the suspect is definitely in the water," he added, though Card, 40, reportedly is the registered owner of two jet-skis and one small recreational boat.

Authorities said helicopters would fly over the river to help direct divers as they search the water, while officers comb the shoreline on foot.

A utility was using its dams to lower the water level in the area to help investigators.

Meanwhile, authorities are chasing up at least 530 tips from the public. It is unusual for US mass shooters not to be caught - dead or alive - at the scene of such attacks.

Mr Sauschuck said they were working to obtain phones, computers and video. He noted that it would also take many more days to process the two crime scenes.

Police executed several search warrants in the suspect's hometown of Bowdoin, a small community beside Lewiston.

Television cameras caught some of that drama on Thursday night on a rural Maine roadway. Police were heard shouting over a megaphone, calling for someone to surrender and come out of a house "with your hands up".

The moment went viral online, but police later clarified it was part of their standard procedure when executing a search warrant.

Police appeared to have moved on to homes and farms in Lisbon on Friday.

Residents of Lewiston, Bowdoin, Lisbon and the neighbouring town of Auburn were living under a shelter-in-place order.

Authorities were discussing whether to lift that mandate, which affects schools and businesses.

The streets of these small New England towns remained empty as the search continued. Armed police were posted at corners while residents stayed home and businesses remain shuttered.

The White House said President Joe Biden had received an update and spoken with FBI Director Christopher Wray, who has committed 200 agents to help state and local police in the inquiry.

"I will ask the community to be as patient as possible with this process," Lewiston Police Chief David St Pierre told the press conference on Friday. "There are many, many moving parts and co-ordination of efforts involved between multiple agencies."

At the same time, Canadian border guards and police in bordering provinces remain on high alert, as there are fears that the suspected gunman could have fled Maine.

Law enforcement officials at Lisbon High School at daybreak