A hot air balloon carrying 32 people, including children, was swept up in a storm and crashed in a fireball outside Slovenia's capital on Thursday, killing four people and injuring 28 others, police and doctors said.

Milan Znidarsic from Ljubljana's Medical Center said four charred bodies were found at the scene of the crash, some 6 miles south of the capital. Znidarsic did not say if any children were among those killed.

The cause of the accident was not immediately clear.

The official STA news agency said two hot air balloons were in the air at the time of the crash. The agency quoted eyewitnesses saying that one of the balloons caught fire while trying to land in a storm. The other balloon landed safely, the report said.

The head of the firefighting team, Tomaz Kucic, said that by the time firefighters got to the scene the balloon was already burning on the ground. Kucic did not specify whether the balloon caught fire while still in the air, or after it crashed.

Znidarsic said that 21 people were admitted in the Ljubljana hospital, while seven more were taken to other hospitals.