Four adults were found dead when police responded to a medical call at a North Dakota property-management business on Monday morning, authorities said.

Investigators are still looking for a suspect and believe the deaths are an isolated incident, Mandan Police Department Chief of Police Jason Ziegler said at a press conference Monday.

Ziegler stressed that authorities have no reason to believe there is a threat to public safety.

Authorities found three men and one woman dead after responding to a medical call at RJR Maintenance and Management at about 7:30 a.m. local time. The victims have not yet been positively identified, according to Ziegler.

Ziegler did not identify how the four victims died but the incident is being treated as a multiple homicide investigation. He also said he could not confirm whether any of the dead were employees of RJR Maintenance and Management.

"A lot of the information you’re going to ask me, I cannot answer," Ziegler said. "It’s very important that our investigators have the ability to follow up and look into leads and everything else before those questions can be answered.”

The police chief asked any business owners and residents in the area to contact investigators with possible video footage or eyewitness accounts.

It was a "rare scene," Ziegler said.

“It’s not something you’d wake up early Monday morning expecting to get the phone call on," he said. "It’s been a long day and it’s going to be a long investigation.”

Mandan police issued a three-sentence statement earlier Monday that said officers had found "several people who were deceased inside" the business in the city of about 22,000 just across the Missouri River from Bismarck.

People with friends or loved ones who work at RJR Maintenance and Management gathered beyond a police line outside the property, anxious for news about those inside, as several hours passed without additional information.

Judy Praus, 70, said she was a longtime friend of the owner's family and had just seen them at a restaurant Saturday. She said she also knew a lot of employees, and had no details on any of them.

"When I was notified, I shattered. Unbelievable," she said.

Gina Kessel, 52, of Mandan, showed up at the business Monday to pick up her son, Mitchell Kessel, an employee there. She said Mitchell "called me, said something is going on." She said he didn't tell her what.

The pair hugged, with both of them crying. Her son declined to comment before going back behind a police line.

A statement posted on the company's website said the business was closed Monday. No one answered the phone at the business, which is somewhat isolated despite its location in a business district near a busy main road known as The Strip. A large empty lot sits in the front, a golf course in back and a soccer complex to one side.

The state Bureau of Criminal Investigation said it was helping with the investigation but did not offer any details.

Darin Helbling, a manager at a nearby bowling alley, said police asked to see his business' surveillance video. Helbling said the video showed only a couple of vehicles on the road that separates the businesses since 10 p.m. Sunday.

RJR's website identified it as a family-owned company that has been handling commercial and residential properties in Bismarck and Mandan for more than 20 years. Its services include collecting rent for landlords, paying mortgages, re-renting apartments, building and grounds maintenance, lawn care, and snow removal. It also rents out storage units.

A "Meet Our Team" feature on the website pictured 22 employees.

Natasha Towne said her brother, Adam Fuehrer, has worked at the business for about eight years. She said she didn't know his status and was frustrated at the lack of news. She declined to talk further.