Scientists in the United States are sounding the alarm after three incidents in three days involving North Atlantic right whales.

Two of the whales were found dead off the coast of Maine, a third was discovered alive but entangled in fishing gear off Cape Cod.

Describing the situation as urgent, the National Oceanic and Atmospheric Administration arranged a conference call with reporters Tuesday.

"When you have something like this, where in a three-day period you lost two valuable members – or contributors – to the population ... that's something we wanted to share with our partners, wanted to share with the public," said David Gouveia, marine mammal program coordinator with the NOAA.

A dead right whale was found Sept. 23 with gear tangled around its head, mouth, flippers and body off the Maine coast near Portland.

"I'd like to see outrage." - Michael Moore

The 13-metre long female was towed into the port and hauled by a logging truck to Gorham, Maine where a necropsy was performed by a team of scientists.

The 11-year-old adult was found to have died following "prolonged and chronic stress" brought on by the entanglement.

A day later, Sept. 24, a second dead right whale was spotted 13 kilometres off Mount Desert Rock, Maine.

In that case there was no sign of entanglement.

Due to the state of decomposition efforts to recover the carcass were abandoned.

Whale freed from gear

It was a happier situation a couple of days earlier when a recreational boater spotted an eight-year-old female right whale entangled in gear off Cape Cod.

A team from the Centre for Coastal Studies quickly found the whale and managed to free much of the gear.

Some of the remaining gear was later found 241 kilometres off Cape Cod.

right whale entangled (international fund for animal welfare)

A right whale entangled in gear in the Bay of Fundy (International Fund for Animal Welfare)

The whale was nowhere to be seen.

"We are optimistic the animal may have shed the gear," said Dave Morin of NOAA's Atlantic Entanglement Response Program.

There are thought to be about 500 North Atlantic right whale in existence.

The population has been described in recent years as "recovering".

But the scientists taking part in Tuesday's conference call believe that recovery is under threat.

"I'd like to see outrage," said Michael Moore, senior research specialist with the Woods Hole Oceanographic Institution.

"Something needs to change and we need to enhance our ability to sustain and maintain the growth of a very endangered species."