The gunman at the centre of a hostage-taking at the Workers' Compensation Board building in downtown Edmonton has surrendered to police without incident.

"All hostages were unharmed," Edmonton police spokesman Dean Parthenis announced.  

The gunman, described as a disgruntled client of the WCB, took eight hostages over the course of the day, according to Insp. Terry Rochhio.

Rochhio would not release the gunman's name, but said the suspect wanted to tell his story.

Police convinced the gunman to let his hostages go one by one throughout the nearly 10-hour ordeal. The last one was set free about 30 minutes before the gunman surrendered.

A 911 call was placed shortly before 9 a.m., reporting that a man with a rifle was inside the building, which is located near the Alberta legislature.

The police tactical unit and officers from the local division descended on the area and began to evacuate hundreds of people from the building, Edmonton police spokesperson Jeff Wuite told CTV News Channel Wednesday morning.

"We've got our negotiator team out here speaking with the man to do our best to bring this to a peaceful conclusion," Wuite said.

Witnesses have told CTV News a loud bang was heard in the building. However it's not clear if the source of the noise was a gunshot.

Shortly after the standoff began, one hostage was released because of a medical issue, reported CTV's Bill Fortier. Other hostages were released throughout the day during negotiations with police.

Those living with the man at an assisted living facility in Edmonton told CTV News he had dealings with the WCB.

A WCB spokesperson also said the board believes the suspect is a claimant.

Don Bellerose, who lives in the same building as the alleged gunman, said no one expected this to happen.

Bellerose said the gunman was working in the concrete industry when he was injured on the job. He said he was then cut off from benefits.

"He's going through a lot of problems right now. In the recent past he has had a lot of problems with workman's compensation, but on top of that his wife is taking him to court for custody of his kids," Bellerose told The Canadian Press. "It's all anger -- all anger."

Bill Moore-Kilgannon, who can see the WCB building from his office in the Public Interest Alberta Society, said heavily armed officers made a brief attempt to enter the building earlier on Wednesday.

"We saw what looked like fairly heavily armed police officers going into the building," Moore-Kilgannon told News Channel. "They didn't stay very long, they were in there maybe three or four minutes and then they came out. Otherwise, there's just a very heavy police presence on all the corners around."

A local radio station is reporting that the man has a grudge against a doctor who works for the board and is "mad at the world."

Jennifer Dagsvik, a WCB spokesperson who was not on site when the incident began, told News Channel that about 700 employees work in the nine-storey building, including case managers and claim adjudicators.

"Our employees know what to do in a case of something like this, but this is just such a rare, rare occurrence," Dagsvik said Wednesday afternoon.

Police have cordoned off several streets in the area and are asking people to stay away from the scene, "simply for their own safety," Wuite said.