Last month, just days after the cruise ship Costa Concordia ran aground off a Tuscan island, killing 17 people and leaving 15 missing, Discovery Channel announced that it would “dissect the anatomy” of the Friday the 13th disaster and — with the quiet confidence of a network long used to being the only game in town — said the docu would air “this spring.”

But on the same day an Italian court refused to lift the house arrest order for the ship’s captain — who is under investigation on suspicion of manslaughter, causing a shipwreck and abandoning the vessel before all passengers were evacuated — National Geographic Channel pounced.

NatGeo announced Tuesday that it had hired the producers of the quick-turnaround British documentary “Terror at Sea: The Sinking of the Concordia” — which already aired on the United Kingdom’s Channel 4 — to rework it for the United States under the name “Italian Cruise Ship Disaster: The Untold Stories.” It will air Sunday, NatGeo announced.

And that beats to air by one week Discovery’s premiere of “Cruise Ship Disaster: Inside the Concordia.”

“Just announced! National Geographic Channel to air first U.S. documentary detailing the Italian cruise ship disaster moment-by-moment,” NatGeo bragged Tuesday.

The Costa Concordia. (CBS NEWS)

Discovery’s Costa Concordia project will be a very focused forensic investigation that uses experts from the Massachusetts Maritime Academy and that includes survivor stories and eyewitness accounts.

Discovery crews will be covering the teams charged with figuring out how to salvage a shipping vessel larger than the Titanic. The Discovery docu will address such questions as: What happened at the time of the accident? What role did captain Francesco Schettin play? How did the crew evacuate the ship? What are the mechanics of searching the site while guarding the waters against environmental damage? What lies next for the massive, unprecedented salvage mission? And will salvage teams be able to save the ship and successfully dismantle its once mighty hull and frame?

“With so many unanswered questions, Discovery will piece together not only the immediate events, but the bigger story of what comes next in recovery and restoration,” Nancy Daniels, executive VP of production and development for Discovery Channel, said recently.

NatGeo’s Concordia program promises to detail the sinking in a “still raw” account, told primarily through the eyes of those who experienced it, who are also American. “American survivors tell their haunting story in depth and share exclusive home video footage,” NatGeo promised.

For the NatGeo telecast, the British documentary’s non-American interviews have been swapped out for American ones: Sameer and Divya Sharma from Massachusetts were celebrating their fifth wedding anniversary, and 18-year-old Amanda Warrick, who was traveling with her older brothers, tossed out the idea on the Friday-the-13th departure date that “something’s gonna happen.”

When the ship hit the rocks, “at first there was a tilt and a shake of the ship — that’s when tables and glasses started crashing. I was kind of in shock. I remember immediately standing up and looking at my brothers. I was just kind of speechless and silent,” Amanda says in the docu.

“It’s really an experiential look at this — what it would be like if you were on” the ship, Michael Cascio, NatGeo exec VP of programming, told The TV Column. “We thought our contribution would be best handled by airing accounts of people who were on it,” including “lots of user-generated video.”

“We’ve used this kind of witness approach before,” Cascio said, noting the channel’s premiere April 13 of the documentary “Witness: Disaster in Japan,” about that country’s earthquake, tsunami and nuclear power plant emergency. That docu aired one month after that disaster.

“When we did the Japanese disaster, and some of these other disasters — it’s a niche to be filled — the news networks have done their bits and pieces, but nobody has put it together,” he said.

In tune with ‘The Voice’

In its second night as The Best Thing to Happen to NBC in Ages, the singing competition series “The Voice” clocked nearly 18 million viewers. That’s NBC’s biggest audience in the Monday 8-to-10 p.m. time slot in five years. That total also puts “The Voice” not far behind Fox’s “American Idol,” which last Wednesday (its stronger night) logged 18.5 million viewers.

Yes, the night before, “The Voice” had enjoyed a post-Super Bowl broadcast and snagged 37 million viewers.  

Following “The Voice” on Monday, NBC’s new highly hyped musical drama, “Smash,” hung on to about 12 million viewers — and the biggest ratings among the prized 18- to-49-year-olds of any regular 10 p.m. drama on any network this season.

 “Idol” exec producer Nigel Lythgoe, who got on the phone with reporters Tuesday to discuss his show, said “The Voice,” as well as Simon Cowell’s “The X Factor,” had created singing-show fatigue among viewers, but he seemed peevish at suggestions that “Idol” was limping along.

“My God, the rest of the world would love these ratings, for God’s sake!” Lythgoe said.

“Let’s hope all of the other shows, like ‘X Factor’ and ‘The Voice,’ continue to be successful for 11 years. I’ll celebrate. . . . I’ll keep my fingers crossed for them,” Lythgoe added.

No, we don’t think anyone believed him.

Asked for his thoughts on “The Voice” this season, Lythgoe pronounced the show “gimmicky” and in need of “stronger talent,” although he said he liked the relationship between judges Blake Shelton and Maroon 5’s Adam Levine, reports The Post’s Emily Yahr.