A Brazilian samba school that highlighted the environmental impact caused by the collapse of a dam has been crowned champions of the Rio de Janeiro carnival.

During its parade, one of Portela's floats depicted the destruction of the River Doce in 2015.

The dam was used to hold waste at an iron ore mine near the city of Mariana.

Portela is Rio's most successful samba school but it had not won the world-famous parade for 33 years.

A panel of judges gave it top marks in most categories, including costumes, rhythm and the quality of the samba song composed for this year's carnival.

Thousands of supporters began celebrating as soon as the final mark was read out at Rio's Sambadrome.

Portela scored 269.9 points to 269.8 for runners-up Mocidade.

One of Rio's most traditional samba schools, it had been eclipsed by younger rivals in the past decades, failing to win the carnival title since 1984.

"The wait is over," said Portela's president, Luis Carlos Magalhaes. "We won't need to mention that anymore."

In this year's parade, Portela focused on The Source of Life: the stories, myths and legends surrounding some of the world's best known rivers, including the Nile and the Mississippi.

It used its floats and the predominantly blue and white costumes of its 3,400 members to develop the story during the 75-minute-long parade.

"We deserved to win, more than anyone else," said Mr Magalhaes. "We worked very hard."