Heavily armed cops have stormed a number of homes linked to a man wanted for killing 18 people as their frantic search for the mass shooter stretches into its second day.

Robert Card, 40, is wanted for murdering 18 people and injuring 13 others in a mass shooting in Lewiston, Maine.

Activity at Card’s last known address led to police storming the house on Thursday night, local time, as cops try to find the mass murderer.

Police said they had detected “activity” at the home and were investigating if Card was hiding inside or nearby.

Loud bangs were earlier heard at a rural property in nearby Bowdoin that police said was linked to Card’s family.

Dozens of officers blocked the road to the home before agents screamed: “FBI - open the door. FBI - come out now.”

His abandoned car was found on Thursday several kilometres from Lewiston with a gun inside, NBC News reported.

Police believe Card may have been looking for his ex-girlfriend when he stormed a bowling alley and bar in the town and opened fire.

Shannon Moss, a spokesman for Maine State Police, said the activity at the Bowdoin property was “part of the investigation”, and said no gunshots were fired.

“Law enforcement is at a home in Bowdoin as part of the investigation into the Lewiston shootings and the search for Robert Card,” she said.

“When it’s appropriate to do so, additional information will be released.

“It’s a tactical operation.”

Police have been searching for Card, a US Army reservist and sergeant described as being an expert marksman. It’s feared he may have fled on a boat he owns.

He had earlier been temporarily committed to a mental health facility over the summer.

Police circulated photographs of Card with a beard and a brown hooded sweatshirt and jeans at one of the crime scenes armed with what appeared to be a semi-automatic rifle.

Public school districts in the area cancelled classes on Thursday and said they would also be cancelled on Friday as police urged residents to stay indoors.

US President Joe Biden, echoing other officials, said in a statement that he mourned “yet another senseless and tragic mass shooting” in a nation where deadly gun violence is commonplace.

He again urged Congress to pass a ban on high-capacity magazines and other gun regulations.

“This is a dark day for Maine,” Governor Janet Mills, a Democrat, said at a press conference.

“Mr Card is considered armed and dangerous and police advise that Maine people should not approach him under any circumstances.”

Police also told residents of Bowdoin, Card’s hometown about 19km east of Lewiston, to shelter in place.

There was an eerie quiet in Lewiston and Lisbon on Thursday, with almost no cars on the roads and just a few people outside. Many downtown businesses appeared to be closed. An illuminated ‘Shelter in Place’ sign was stationed on Lewiston’s Main Street.

Card is a petroleum supply specialist at the Army Reserve base in Saco, Maine, who had never been deployed in combat since enlisting in 2002, the US Army said.

A Maine law enforcement bulletin described Card as a trained firearms instructor who recently said that he had been hearing voices and had other mental health issues.

He threatened to shoot up the National Guard base in Saco and was “reported to have been committed to mental health facility for two weeks during summer 2023 and subsequently released,” according to the bulletin from the Maine Information & Analysis Centre, a unit of the state police. Reuters could not confirm the details reported in the bulletin.

The attacks began shortly before 7pm, local time, at the Just-In-Time Recreation bowling alley, where one female patron and six males were shot dead, police said, without giving the victims’ ages.

Within about 10 minutes, they received reports of a shooting at Schemengees Bar & Grille Restaurant, about five kilometres away. Eight males were fatally shot dead there, police said.

Three victims who were taken to hospitals later died of their injuries. A further eight are in a critical condition.

Guns are lightly regulated in Maine, a largely rural state near the northeast border with Canada where about half of all adults live in a household with a gun, according to a 2020 study by RAND Corporation.

Maine does not require a permit to buy or carry a gun, and it does not have so-called “red flag” laws seen in some other states that allow law enforcement to temporarily disarm people deemed to be dangerous.

Biden has spoken to state officials to offer the federal government’s support and ordered flags to be flown at half-mast until Monday to honour the victims, his office said.

The 18 fatalities in the shootings on Wednesday is close to the annual number of homicides that normally occur in Maine, which has fluctuated between 16 and 29 since 2012, according to Maine State Police.