One person was killed and 13 others were wounded when a bomb exploded in a red-light district in Puerto Berrio, a city in the northwestern Colombian province of Antioquia, emergency management officials said.

The bomb went off Monday inside a business, killing a 47-year-old woman, Antioquia emergency management office operations coordinator Gilberto Meza said.

Six of the people wounded by the blast were airlifted to Medellin, the capital of Antioquia, and are listed in serious condition, Meza said.

The other seven victims, including a 10-year-old boy and another child, were treated at medical facilities near the scene of the bombing.

The bombing is under investigation and officials have not ruled out that it was the work of illegal armed groups.

The attack may have been carried out as vengeance, officials said, adding that a grenade may have been used by the assailants.