LEWISTON, Maine — Police were conducting a massive search for a firearms instructor early Thursday after a mass shooting at two locations in Maine’s second-biggest city killed at least 16 people and wounded dozens more, according to law enforcement officials.

The Lewiston area was under a lockdown as hundreds of law enforcement officers searched for 40-year-old Robert R. Card, who was identified as a “person of interest.’’ Officials told people to “stay inside with doors locked.’’

“Card is considered armed and dangerous,’’ Mike Sauschuck, commissioner of the Maine Department of Public Safety, said at a news conference near midnight.

Other news outlets reported an even higher death toll and put the number of wounded at more than 50. Sauschuck declined to confirm the number of dead.

“This is a very fluid situation,’’ he said.

A vehicle connected to Card had been located by police in Lisbon, a neighboring town southeast of Lewiston. A search was underway in Lisbon for “a suspect believed to have been involved’’ in the shootings, Lisbon police said in a Facebook post late Wednesday night.

The Associated Press, citing a document circulated by law enforcement officials, said Card is a firearms instructor trained by the military and was recently in a mental health facility. He had been committed to the facility for two weeks during the summer, according to the AP.

Earlier, around 9 p.m., Lewiston police posted images of a suspect: a bearded man in a sweatshirt and cargo pants holding a rifle against his shoulder. The photos appeared to be stills from security camera footage.

The shootings occurred at the Sparetime Recreation bowling alley and Schemengees Bar & Grille, located just over 4 miles apart in Lewiston, Maine’s second largest city and the home of Bates College. Sauschuck said the shootings occurred at 6:56 p.m.

Melinda Small, the owner of Legends Sports Bar and Grill, about a quarter mile from the bowling alley, told the Associated Press that her staff locked their doors around 7 p.m. after hearing about the shooting from a customer.

“I am honestly in a state of shock,’’ she said.

Justin Juray, an owner of Sparetime Recreation, told The New York Times that there were about 100 to 150 people, including 20 children, at the bowling alley at the time of the shooting.

The Lewiston Sun Journal reported that police converged on the bowling alley around 7:15 pm. Around the same time, they received reports of another shooting at the bar four miles away.

Then the Maine State Police posted on X, formerly called Twitter, that there was “an active shooter in Lewiston.’’

At 8:09 p.m., Bates College sent a text message to students via an emergency alert system advising them to stay indoors, the campus student newspaper reported.

Around the same time, the Lewiston police posted on Facebook that the department was “currently dealing with an active shooter incident.’’

“Please stay off the roads to allow emergency responders access to the hospitals,’’ the department said in its post.

Later, the Central Maine Medical Center issued a statement saying the center was “reacting to a mass casualty, mass shooter event.’’ The center could not provide any specifics on the number of casualties.

“Central Maine Healthcare is coordinating with area hospitals to take in patients,’’ the statement from Central Maine Medical Center said.

There was a heavy police presence outside the hospital grounds. Eric Bilodeau, an officer with the Sanford Police Department, was posted near an entrance to the emergency room.

He said he had been out for a birthday dinner with his mother when he saw enough police vehicles pass by to know something was wrong.

“There were one too many sirens,’’ he said.

He had been at the hospital since around 8 p.m., he said. During the next three hours, he saw a number of helicopter ambulances come and go, he said.

Lewiston remained under a shelter-in-place order after 9 p.m., according to Shannon Moss, the public information officer for the Maine Department of Public Safety.

The White House press office said that President Biden had been informed of the shooting and “will continue to receive updates.’’

FBI agents in Boston were on standby to assist with the investigation, a spokesperson said.

“The FBI Boston Division continues to coordinate with our local, state, and federal law enforcement partners in Maine and we stand ready to assist with any available resources they need, including evidence response, investigative and tactical support, as well as victim assistance,’’ spokesperson Kristen Setera said.

“We continue to urge the public to remain vigilant and report any and all suspicious activity and/or individuals to law enforcement immediately,’’ Setera said via email.

Lewiston Mayor Carl L. Sheline said he is “heartbroken for our city and our people.’’

“Lewiston is known for our strength and grit and we will need both in the days to come,’’ Sheline said.

Material from the Associated Press was used in this report. Mike Damiano can be reached at mike.damiano@globe.com. Sabrina Shankman can be reached at sabrina.shankman @globe.com.