BALTIMORE (WJZ) — A fire broke out at the city jail in downtown Baltimore on Thursday morning, according to authorities.

The fire started on the fifth floor, a spokesperson for the Baltimore City Fire Department said.

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Inmates were ordered to shelter in place as firefighters tackled the flames, the spokesperson said.

No inmates were injured by the fire. The source of the fire is not yet known, according to authorities.

A union representing correctional officers said smoke from the fire spread to multiple floors due to the poor ventilation in the facility.

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This is the second time that firefighters have been sent to the jail to extinguish a fire within the past six months.

In January, inmates set at least five fires in a Baltimore prison. More than 30 people were treated for smoke inhalation following the fires.

That month, inmates started three fires in the common area of the fifth floor. They set fire to paper products, clothing and a plastic rolling food cart.

New fires ignited while investigators were responding to the first three fires.

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Inmates on another floor reportedly set two more fires using including clothes and another food cart.

CBS Baltimore Staff