LISBON, Portugal -- Emergency services say a high-speed intercity train rear-ended a local train waiting to enter a station in central Portugal, slightly injuring 21 people.

The collision late Monday derailed several carriages and left a pile of wreckage on Portugal's main north-south line.

Officials said the local train was waiting to pull into a station near Coimbra, 200 kilometres north of the capital, Lisbon, when the northbound intercity train slammed into it from behind at 9:15 p.m. (2115 GMT).

Transport Minister Alvaro Santos Pereira said Tuesday he had ordered an inquiry into the causes and expected a preliminary report within three days.