Police are still searching for a gunman who killed 18 people and injured many more at a bowling centre in Lewiston in the US state of Maine.

FBI

The gunman opened fire at around 7pm on Wednesday evening at the Just-in-Time Recreation bowling alley and then the Schemengees Bar & Grille. Surveillance footage showed the shooter, who is believed to be 40-year-old army reservist Robert Card.

An intensive manhunt began after he was formally identified as the suspect in the now active homicide investigation during a press conference on Thursday morning.

The bowling alley posted on Facebook: "None of this seems real, but unfortunately it is. We are devastated for our community and our staff. We lost some amazing and whole-hearted people from our bowling family and community last night. 

"There are no words to fix this or make it better. We are praying for everyone who has been affected by this horrific tragedy. We love you all and hold you close in our hearts."

Maine residents kept to their homes for a second night on Thursday as hundreds of heavily armed police and FBI agents searched intensely for Card.