A prison officer is unharmed and "doing well" after being taken hostage by two prisoners in Hobart's Risdon Prison, the United Voice Union says.

Just before 11:00am Tasmania Police and the Justice Department both confirmed they were responding to an incident at the prison.

The ABC understands two inmates armed with improvised knives, known as 'shivs', took a prison guard into a room.

The United Voice Union confirmed one of its members was taken hostage at the prison and that the situation was resolved quickly and without police involvement.

Jannette Armstrong from the union said the guard was not hurt and, despite the traumatic experience, was doing well.

No other staff or inmates were injured.

Ms Armstrong said several staff members witnessed the incident.

She said it had been a "very difficult few months at the prison service" following three deaths in custody in the past two months as well as increasing tensions amongst prisoners due to a smoking ban at the facility.

Former prison officer Tony Burley said the division where the incident took place is a dangerous area.

"In that particular unit, you have 26 prisoners with two officers looking after them during the day," he said.

An ambulance was seen leaving the scene but the Justice Department confirmed no-one was injured.

Security officers are guarding the front gates, restricting access, and the prison appears to be in lockdown, with no inmates visible in the exercise areas.

The Justice Department later released a statement about the incident:

Risdon Prison Complex is returning to normal operations after an incident involving a correctional officer and two prisoners in the Derwent unit earlier this morning. No staff or prisoners were injured during the incident. Tasmania Police have arrived on site to begin their inquiries. The Director of Corrective Services would like to thank staff for their professional response and handling of this incident across the service. In accordance with standard post-incident protocols, staff and prisoners will be offered support and assistance.

Deputy Premier Jeremy Rockliff said there would be a full investigation into the incident.

"Any incident like this we take extremely seriously," he said.

"We're dealing with a very volatile and complex situation, as you would well appreciate, and we can learn from an incident like today and we will."