International scientists working at an astronomical observatory in Chile's northern Atacama desert have for the first time detected a supermassive black hole feeding on cold gas, a university in Mexico says.

Scientists have long known black holes feed on hot gas to gain mass, but the discovery marks the first time researchers have "directly observed" the phenomenon with cold gas.

"A team of international astronomers ... discovered that in addition to feeding on very hot gas, black holes can also 'pig out' on giant molecular clouds of very cold gas in the shape of a clumpy and chaotic downpour," the National Autonomous University said in a press release on Monday.

The team includes Roberto Galvan from UNAM's Radioastronomy and Astrophysics Institute, located in Morelia, in Mexico's central state of Michoacan.

"Like people, black holes grow according to what they ingest," said UNAM. "Some measure 10 million times the mass of the Sun and others 500 million, which poses the question, how do they attain their size?"

Following the discovery, scientists "now know that in 'feeding', they combine processes, vary their 'diet' and 'eat' hot and cold gas," the university said.

"That's the contribution of this study, which offers direct observation that a particular black hole is gobbling up clouds of cold gas," said Galvan.

The supermassive black hole is estimated to be "100 times larger than our galaxy, 300 million times the mass of the Sun," said UNAM.

The discovery was published earlier this month in the magazine Nature, under the headline "Cold, clumpy accretion onto an active supermassive black hole."

The black hole researchers observed is located a billion light years away from Earth, at the center of what is known as the Brightest Cluster Galaxy.

Astronomers are "more or less convinced that almost any galaxy, including the Milky Way, has a supermassive black hole at its center," said Galvan, and they calculate that ours has 3 million times the mass of the Sun.

The Atacama Large Millimeter/submillimeter Array (ALMA) of radio telescopes is part of an international partnership to advance scientific research of the Milky Way galaxy.