A Romanian museum is analysing ashes found in a stove to see if they are the remains of seven paintings by Picasso, Matisse, Monet and others that were stolen last year from the Netherlands, an official has said.

The prosecutor's spokeswoman, Gabriela Chiru, told Associated Press that Romania's National History Museum was examining the ashes found in the stove of Olga Dogaru. She is the mother of Radu Dogaru, one of three Romanian suspects charged with stealing the paintings from Rotterdam's Kunsthal gallery in a daytime heist.

It was the biggest art theft in more than a decade in the Netherlands. The stolen works have an estimated value of tens of millions of dollars if they were sold at auction.

Dogaru told investigators she was scared for her son after he was arrested in January and buried the art in an abandoned house and then in a cemetery in the village of Caracliu. She said she later dug them up and burned them in February after police began searching the village for the stolen works.

Chiru indicated that authorities did not necessarily believe Dogaru's account. She said it could take months for the results of the tests to be known.

Thieves broke into the museum on 16 October through a rear emergency exit, took the paintings from the wall and fled, all within two minutes.

Police who arrived less than five minutes after the break-in triggered an alarm found nothing but empty spaces on the walls, broken hanging wires and tyre tracks in grass behind the gallery.

The stolen paintings were: Picasso's 1971 Harlequin Head; Monet's 1901 Waterloo Bridge, London and Charing Cross Bridge, London; Matisse's 1919 Reading Girl in White and Yellow; Paul Gauguin's 1898 Girl in Front of Open Window; Meyer de Haan's Self-Portrait, around 1890; and Lucian Freud's 2002 work Woman With Eyes Closed.

Radu Dogaru, the alleged ringleader, remains in custody along with two other suspects as investigators seek the paintings and other evidence.

The stolen paintings came from the private Triton Foundation, a collection of avant-garde art put together by multimillionaire Willem Cordia, an investor and businessman, and his wife, Marijke Cordia-Van der Laan. Cordia died in 2011.