Shortly after 6 pm, the rescue service was alerted to a traffic accident on Mälarvägen in Eskilstuna.
Two cars are said to have collided, one of them with horse transport.
The transport trolley must have overturned and the damage to the horse is unclear.
- It seems to have injured the leg.
A veterinarian is on his way to the scene, says Roger Ehrstedt, internal officer at the rescue service.
The accident has caused traffic jams.
According to the Swedish Transport Administration's forecast, the problem may have been rectified by 7 p.m.