Dead whales keep washing up along the East Coast. What's going on?

Twelve whales have washed up on Atlantic Coast beaches since Dec. 1, but marine mammal experts and some conservation groups urge caution before jumping to

conclusions about why these animals and others died. In total, at least18 marine mammals from five species — including humpbacks, pilot whales and an orca —

have been found dead on beaches from Maine to Florida since Nov. 28. The deaths have prompted concerns as photos and stories of the whales and marine mammal

rescue teams circulate online. On Wednesday, federal officials held a conference call with reporters to try to address swirling questions and rumors.  Start the day smarter.

Get all the news you need in your inbox each morning. Final results of their investigations aren’t yet available. Based on preliminary reports, it’s likely a

variety of human activities may be responsible for some of the deaths. Here’s what is known so far:   How unusual is it to have so many dead

whales?  Whale deaths overall have been unusually high for years, with an upward trend in deaths along the East Coast, said Gilbert Brogan, a program manager with

Oceana, a nonprofit ocean advocacy group. The National Marine Fisheries Service is in the midst of three separate investigations into an increase in deaths

among Atlantic Coast whales. Fisheries service officials also noted that humpback whales are rebounding to some extent in the mid-Atlantic. Increasing

populations can put the animals at greater risk of interactions with boats and fishing gear.