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KNOW IT ALL: Tuesday's Top Stories at NBC News

From the rising death toll in the sunken Korean ship disaster to security concerns caused by the airline stowaway, see the stories we're following.

Good morning, and happy Earth Day! Here are some of the stories we're following today:

1. More grim details and bodies emerge from sunken ship

The death toll passed 100 earlier today with nearly 200 people still missing after the vessel carrying mostly high school students capsized off the coast of South Korea last week. New reports say that only two of the ship’s 46 lifeboats were deployed during the accident, and South Korea’s president has called the captain’s delay to get passengers off the ship “unforgivable, murderous behavior.” Read more in NEWS.

NBC News' Bill Neely is in South Korea:

2. Teen stowaway on 5-1/2-hour flight: How did he do it?

The 16-year-old boy who miraculously survived a trip from California to Hawaii after sneaking into the plane’s wheel well has raised several questions about airport security. Authorities say the teen was able to hop a fence at about 1 a.m. Sunday at Mineta San Jose International Airport, and then climb into the plane’s wheel well undetected by security. Read more in NEWS.

3. Biden tells Ukrainian government the U.S. is ‘ready to assist’

Vice President Joe Biden brought a message of support during his visit to Ukraine on Monday in what is so far the highest-level U.S. visit since the pro-West government gained a foothold earlier this year. Biden’s visit comes after a tentative agreement last week between the U.S., Ukraine, Russia and the European Union to end the violence in the country’s eastern region. Read more in NEWS.

4. Sub will continue search for missing jet beyond target area

The unmanned submarine searching for the missing Malaysian jet is more than 80 percent done, officials said, but that doesn’t mean it will stop looking once the current search zone is fully swept. Authorities are under pressure to figure out their next course of action and find the plane, which disappeared more than six weeks ago. Read more in NEWS.

5. American man runs away with Boston Marathon title

For the first time since 1983, an American man has won the Boston Marathon. Eritrean-American Meb Keflezighi won with a time of 2:08:37, crossing the finish line a mere 11 seconds over Kenyan rival Wilson Chebet. “Boston Strong. Meb Strong,” Keflezighi later said. “I was going to give everything I had for the people.” Security at Monday’s marathon was tight after last year’s bombing, and no major incidents were reported. Read more at NBC SPORTS.

6. Sherpa guides call for more protections after deadly disaster

Nepal’s ethnic Sherpa community, which assists adventurers who want to climb Mount Everest, are pressing the government for more insurance and regulations following last week’s avalanche that killed at least 13 of the guides. The Sherpas may even consider a boycott, which could disrupt the start of the climbing season just days away. Read more in NEWS.

… What’s trending today?

Look out Snoop Dogg, B-Willy is sippin’ on your gin and juice.

“NBC Nightly News” anchor Brian Williams is the star of another rap video courtesy of “The Tonight Show Starring Jimmy Fallon” — and this time it’s the Snoop Dogg classic “Gin and Juice.”

Previously, Williams and other NBC personalities popped up on an edited version of “Rapper’s Delight.” Fallon debuted the video on Monday night’s “Tonight Show.”