Bolivian police are investigating exploding envelopes that wounding seven people, three of them severely, in La Paz.

Bolivian police commander Victor Hugo Escobar says the first explosion, at a construction company, has seriously injured firefighters called in to deactivate the device. A second explosion at a bus terminal has severely wounded the wife of a union leader with close ties to President Evo Morales.

Arminda Colque is the wife of union leader Fidel Surco. She has lost three fingers, is seriously burned and may not be able to see again. Two firefighters are in intensive care.

It was unclear what may have motivated the Wednesday attacks.