An urgent police dragnet entered its second day late Thursday for a man accused of gunning down 18 people at a bowling alley and a bar in Maine, United States.

Dozens of law enforcement agents surrounded the family home of 40-year-old suspect Robert Card, but by mid-evening agents left the property in Bowdoin, near Lewiston, to hunt for him elsewhere.

A wide area around Lewiston remained locked down more than 24 hours after Card allegedly went on a rampage, culminating in the deadliest mass shooting this year in America. Thirteen people were also wounded.

Authorities erected roadblocks, ordered schools and businesses closed, and told residents to stay indoors.

Governor Janet Mills said the suspect was "considered armed and dangerous, and police advised that Maine people should not approach him under any circumstances."

Card was seen in surveillance footage pointing a semi-automatic rifle as he walked into the Just-in-Time bowling alley on Wednesday.

News outlets broadcast footage of people fleeing in terror from the bowling alley after the shooting started Wednesday evening.

Card is a member of the US Army Reserve. US media reported that he had recently been sent for psychiatric treatment after he said he was hearing voices.

Hundreds of police in military-style camouflage gear and Federal Bureau of Investigation agents flooded the search zone in what Lewiston police chief David St. Pierre called "an all-hands-on-deck approach."

Biden called Maine's governor to offer federal support, and ordered flags to be lowered to half-staff at the White House and all government buildings.