NEW YORK -- In a sign of a rapidly changing media world, a relatively unknown New York-based online non-profit news site joined some of the country's most well-known media outlets in claiming a Pulitzer Prize, the highest honour in journalism.

InsideClimate News won the Pulitzer Monday for national reporting for its reports on problems in the regulation of the nation's oil pipelines. Founded five years ago, InsideClimateNews reports on energy and the environment. Writers Lisa Song, Elizabeth McGowan and David Hasemyer were recognized for a project that began with an investigation into a million-gallon spill of Canadian tar sands oil into the Kalamazoo River in Michigan in 2010. The reporters went on to look more broadly at pipeline safety and the particular hazards of a form of oil called diluted bitumen, or "dilbit."

"I think it's a very hopeful sign. I think it really shows the way the journalism ethos reconfigures itself as times change," said Sig Gissler, the administrator of the prizes.

"This is a different way for journalists to practice their trade and make a contribution," McGowan said. "The fourth estate has lost a lot. This is a way we're making a gain."

The Pulitzers, journalism's highest honour, are given out each year by Columbia University on the recommendation of a board of journalists and others. Each award carries a $10,000 prize except for the public service award, which is a gold medal.

The Associated Press received the award in breaking news photography for its coverage of the civil war in Syria.

The Sun Sentinel of Fort Lauderdale, Fla., received the public service award for an investigation of off-duty police officers' reckless driving, and longtime Pulitzer powerhouses The Wall Street Journal and The Washington Post were recognized for commentary and criticism, respectively.

The Star-Tribune of Minneapolis captured two awards, for local reporting and editorial cartooning.

Cheers erupted in the Denver Post's newsroom when word came that the newspaper had won the Pulitzer in the breaking news category for its coverage -- via text, social media and video -- of the movie theatre massacre in Aurora, Colo., that killed 12 people during a midnight showing of a new Batman movie last summer.

The honour was bittersweet for some, and people teared up and shared hugs.

"We are part of this community. The tragedy touches us, but we have a job to do," said Kevin Dale, the Post's news director.

The New York Times' David Barstow and Alejandra Xanic von Bertrab won the investigative reporting award for stories that detailed how Wal-Mart Stores Inc. systematically bribed Mexican officials with millions of dollars to get permission to build several stores across the country. The Times' reporting spurred federal investigations.

The Times' David Barboza received the international reporting award for his look at a how a "Red Nobility," made up of relatives of top Chinese officials, has made fortunes in businesses closely tied to the government.

The Times staff won the explanatory reporting award for looking at the business practices of Apple Inc. and other technology companies and illustrating "the darker side of a changing global economy for workers and consumers," the judges said.

In the feature writing category, John Branch of the Times won for a gripping narrative of an avalanche that trapped 16 skiers and snowboarders in the Cascade Mountains of Washington state. Told through photos, video, graphics and magazine-style text, the piece was lauded in the industry as setting a new standard for multimedia journalism.

The paper's editors "view the wonderful bounty of prizes as a real tribute to the newsroom's excellence and dedication," Executive Editor Jill Abramson told the staff.

The AP's Rodrigo Abd, Manu Brabo, Narciso Contreras, Khalil Hamra and Muhammed Muheisen were recognized for "producing memorable images under extreme hazard" while covering the Syrian war, the judges wrote.

Their images depict the dazed and weeping wounded; a heartbroken man cradling the body of his bloodied, barefoot son; a sobbing, fatherless child; an 11-year-old aiming a toy rocket-propelled grenade.

AP Director of Photography Santiago Lyon called the winners "some of the bravest and most talented photographers in the world."

The same conflict was the subject of the winning entry in feature photography. Javier Manzano, a freelance photographer, won for an image of two rebel soldiers guarding their position as light streams through bullet holes in a nearby wall. The photograph was distributed by Agence France-Presse.

At the Sun Sentinel, reporters explored speeding by off-duty officers. The reporting led to suspensions, firings and police policy changes.

"It feels great to win for that story because it really changed things here for the better," Editor Howard Saltz said.

At the Star Tribune, Brad Schrade, Jeremy Olson and Glenn Howatt captured the Pulitzer for local reporting for examining a sharp rise in in infant deaths at day-care centres, reporting that spurred stronger regulation. Minnesota authorities reported last week that day care deaths have dropped significantly.

It was "really satisfying we had an impact," Schrade said.

Steve Sack, who has been at the paper for 35 years, won for editorial cartooning.

In opinion writing categories, Bret Stephens of The Wall Street Journal received the commentary award for columns on American foreign policy and domestic politics.

The Washington Post's chief art critic, Philip Kennicott, was honoured for writing on the sociology of images. In one case, he focused on a picture of President Barack Obama and first lady Michelle Obama hugging, calling it a portrait of a modern marriage.

The editorial writing award went to Tim Nickens and Daniel Ruth of the Tampa Bay Times for a series of editorials that helped reverse a decision to end fluoridation of the water supply in Pinellas County, home to 700,000 people. Formerly the St. Petersburg Times, the newspaper is owned by the non-profit Poynter Institute.

Adam Johnson's "The Orphan Master's Son," about a man's travails in North Korea, won the Pulitzer Prize for fiction.

Other arts winners included Ayad Akhtar winning the drama prize for "Disgraced," a play about a successful Pakistani-American lawyer whose dinner party spins out of control amid a heated discussion of identity and religion.

The history prize went to Frederik Logevall for "Embers of War: The Fall of an Empire and the Making of America's Vietnam," about Vietnam under the French.

Tom Reiss won the biography prize for "The Black Count: Glory, Revolution, Betrayal and the Real Count of Monte Cristo." He learned he won the Pulitzer while visiting the dentist, who waived the usual fee.

Sharon Olds' chronicling of her divorces in her 12th poetry collection, "Stag's Leap," won her the Poetry prize. "I'm in shock," she said Monday when reached by phone, adding that she was trembling and a "little weepy.

"And my eyes are very open and sticky."

The general nonfiction Pulitzer went to Gilbert King for "Devil in the Grove: Thurgood Marshall, the Groveland Boys, and the Dawn of a New America." The book tells the story of a 1949 case, in which four black men were falsely accused of rape, and their attorney was Thurgood Marshall.

Caroline Shaw's composition "Partita for 8 Voices" took the music prize. The 30-year-old graduate student at Princeton University is also a violinist and a vocalist.