The train derailed due to a landslide in Vacarisses, between the north-eastern towns of Terrassa and Manresa.
It crashed at about 6.15am local time on Tuesday morning. The train was about 30 miles from Barcelona, its destination.
Of the 44 injured people, five were taken to hospital. Their conditions were unknown.
The train was made up of six wagons and 131 people were on board.
Pictures from the scene appeared to show at least four of the carriages had derailed.
Fourteen fire engines and 11 ambulances were called to free passengers trapped in the wreckage.
Spanish railway operator spokesman Antonio Carmona told local media that heavy rain in the area over the past few days could have caused the landslide.
Miquel Buch, Catalonia's minister of the interior, visited the scene on Tuesday as the authorities surveyed the wreckage.
Recent downpours have battered Spain. A woman died on Sunday after a river flooded its banks in the north-western Galicia region.
And on Monday, huge waves swept away the balconies of a sea-side apartment building on the Canary island of Tenerife.
In 2013, 79 people were killed and about 140 injured when a train travelling from Madrid to north-west Spain came off the tracks. It was Spain's worst train crash for decades.
This page is being updated.
