A ninth dead whale has washed up on the New Jersey coastline, as conservationists and local authorities investigate the causes of an unusual number of such deaths along the US east coast.

The humpback was found in Manasquan, New Jersey, on Monday.

The whale was removed from the beach on Tuesday and taken to the county landfill for a necropsy and to collect tissue samples, a spokesperson for Noaa Fisheries, part of the National Oceanographic and Atmospheric Administration, told Gothamist.

The whale is one of many recently found dead off New York and New Jersey. At least 10 humpback whales have died in east coast waters in 2023, six near New York and New Jersey, CBS reported.

Noaa Fisheries is investigating the cause of such “unusual mortality events”, data for which has been collected since 2016.

Conservatives and some conservationist activists attribute the rise in deaths to increasing offshore wind projects, calling on federal authorities to do more to protect the coastline.

But federal officials have pushed back against claims that wind turbines are to blame, saying evidence does not support the contention wind energy projects cause whale fatalities.

Noaa Fisheries said: “[T]here is no evidence to support speculation that noise resulting from wind development-related site characterization surveys could potentially cause mortality of whales, and no specific links between recent large whale mortalities and currently ongoing surveys.”

Local whale recovery and animal welfare organizations have faced threats, over accusations that they are “hiding” wind turbine-caused deaths, Time reported.

Sheila Dean, 75, from the Marine Mammal Stranding Center in New Jersey, said one resident accused the center of covering up whale deaths.

“He just starts [yelling], ‘I want to know, I demand to know,’” Dean said. “He was very frightening.”

Humpback whale strandings have been increasing for seven years. Of 178 east coast whale deaths scientists examined, 40% were caused by ships or whales becoming entangled in fishing gear.

Under the Biden administration, offshore wind projects have been initiated off New Jersey in an effort to create 30 gigawatts of energy by 2030, CBS reported.

At least 12 New Jersey mayors have written to their state congressional delegation, calling for a pause on offshore wind activities until “further investigation is held by federal and state agencies that determine these activities are not a contributing factor to recent whale deaths”.

A rally to demand that the New Jersey governor, Phil Murphy, pause all wind turbine projects will be held by an activist group, Protect Our Coast NJ, on Sunday.