Is offshore wind development a threat to whales? Here's what to know.

In less than two months, seven dead whales have washed up on the shores of New Jersey and New York. What's behind the mortalities has not been clearly established, but theories abound. Some have pointed blame at offshore wind development in the region and claimed construction of the sites causes harm to marine animals. But federal officials are pushing back, saying that's not what the evidence shows.

Here's what we know about the recent whale deaths and what researchers say could be the cause.